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Author name code: appourchaux
ADS astronomy entries on 2022-09-14
author:"Appourchaux, Thierry"
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Title: Solar-like oscillations and ellipsoidal variations in TESS
observations of the binary 12 Boötis
Authors: Ball, Warrick H.; Miglio, Andrea; Chaplin, William J.;
Stassun, Keivan G.; García, Rafael; González-Cuesta, Lucia; Mathur,
Savita; Appourchaux, Thierry; Benomar, Othman; Buzasi, Derek L.;
Jiang, Chen; Kayhan, Cenk; Örtel, Sibel; Orhan, Zeynep Çelik;
Yıldız, Mutlu; Ong, J. M. Joel; Basu, Sarbani
2022MNRAS.tmp.2121B Altcode: 2022arXiv220802302B
Binary stars in which oscillations can be studied in either or both
components can provide powerful constraints on our understanding
of stellar physics. The bright binary 12 Boötis (12 Boo) is a
particularly promising system because the primary is roughly 60 per
cent brighter than the secondary despite being only a few per cent
more massive. Both stars have substantial surface convection zones
and are therefore, presumably, solar-like oscillators. We report
here the first detection of solar-like oscillations and ellipsoidal
variations in the TESS light curve of 12 Boo. Though the solar-like
oscillations are not clear enough to unambiguously measure individual
mode frequencies, we combine global asteroseismic parameters and a
precise fit to the spectral energy distribution (SED) to provide new
constraints on the properties of the system that are several times more
precise than values in the literature. The SED fit alone provides new
effective temperatures, luminosities and radii of 6115 ± 45 K, 7.531
± 0.110 L<SUB>⊙</SUB> and 2.450 ± 0.045 R<SUB>⊙</SUB> for 12 Boo
A and 6200 ± 60 K, 4.692 ± 0.095 L<SUB>⊙</SUB> and 1.901 ± 0.045
R<SUB>⊙</SUB> for 12 Boo B. When combined with our asteroseismic
constraints on 12 Boo A, we obtain an age of $2.67^{+0.12}_{-0.16}\,
\mathrm{Gyr}$, which is consistent with that of 12 Boo B.
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Title: The on-ground data reduction and calibration pipeline for
SO/PHI-HRT
Authors: Sinjan, J.; Calchetti, D.; Hirzberger, J.; Orozco Suárez,
D.; Albert, K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero,
A.; Blanco Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero,
L.; Gutierrez Marquez, P.; Kahil, F.; Kolleck, M.; Solanki, S. K.; del
Toro Iniesta, J. C.; Volkmer, R.; Woch, J.; Fiethe, B.; Gómez Cama,
J. M.; Pérez-Grande, I.; Sanchis Kilders, E.; Balaguer Jiménez,
M.; Bellot Rubio, L. R.; Carmona, M.; Deutsch, W.; Fernandez-Rico,
G.; Fernández-Medina, A.; García Parejo, P.; Gasent Blesa, J. L.;
Gizon, L.; Grauf, B.; Heerlein, K.; Korpi-Lagg, A.; Lange, T.; López
Jiménez, A.; Maue, T.; Meller, R.; Michalik, H.; Moreno Vacas, A.;
Müller, R.; Nakai, E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub,
J.; Strecker, H.; Torralbo, I.; Valori, G.
2022arXiv220814904S Altcode:
The ESA/NASA Solar Orbiter space mission has been successfully launched
in February 2020. Onboard is the Polarimetric and Helioseismic Imager
(SO/PHI), which has two telescopes, a High Resolution Telescope
(HRT) and the Full Disc Telescope (FDT). The instrument is designed
to infer the photospheric magnetic field and line-of-sight velocity
through differential imaging of the polarised light emitted by the
Sun. It calculates the full Stokes vector at 6 wavelength positions
at the Fe I 617.3 nm absorption line. Due to telemetry constraints,
the instrument nominally processes these Stokes profiles onboard,
however when telemetry is available, the raw images are downlinked and
reduced on ground. Here the architecture of the on-ground pipeline
for HRT is presented, which also offers additional corrections not
currently available on board the instrument. The pipeline can reduce
raw images to the full Stokes vector with a polarimetric sensitivity
of $10^{-3}\cdot I_{c}$ or better.
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Title: The magnetic drivers of campfires seen by the Polarimetric
and Helioseismic Imager (PHI) on Solar Orbiter
Authors: Kahil, F.; Hirzberger, J.; Solanki, S. K.; Chitta, L. P.;
Peter, H.; Auchère, F.; Sinjan, J.; Orozco Suárez, D.; Albert,
K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco
Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutiérrez
Márquez, P.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.;
Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis
Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti,
D.; Carmona, M.; Deutsch, W.; Fernández-Rico, G.; Fernández-Medina,
A.; García Parejo, P.; Gasent-Blesa, J. L.; Gizon, L.; Grauf, B.;
Heerlein, K.; Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.;
Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai,
E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.;
Torralbo, I.; Valori, G.; Aznar Cuadrado, R.; Teriaca, L.; Berghmans,
D.; Verbeeck, C.; Kraaikamp, E.; Gissot, S.
2022A&A...660A.143K Altcode: 2022arXiv220213859K
Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter
(SO) spacecraft observed small extreme ultraviolet (EUV) bursts,
termed campfires, that have been proposed to be brightenings near the
apexes of low-lying loops in the quiet-Sun atmosphere. The underlying
magnetic processes driving these campfires are not understood. <BR
/> Aims: During the cruise phase of SO and at a distance of 0.523
AU from the Sun, the Polarimetric and Helioseismic Imager on Solar
Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI,
offering the possibility to investigate the surface magnetic field
dynamics underlying campfires at a spatial resolution of about 380
km. <BR /> Methods: We used co-spatial and co-temporal data of the
quiet-Sun network at disc centre acquired with the High Resolution
Imager of SO/EUI at 17.4 nm (HRI<SUB>EUV</SUB>, cadence 2 s) and the
High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5
min). Campfires that are within the SO/PHI−SO/EUI common field
of view were isolated and categorised according to the underlying
magnetic activity. <BR /> Results: In 71% of the 38 isolated events,
campfires are confined between bipolar magnetic features, which seem to
exhibit signatures of magnetic flux cancellation. The flux cancellation
occurs either between the two main footpoints, or between one of the
footpoints of the loop housing the campfire and a nearby opposite
polarity patch. In one particularly clear-cut case, we detected the
emergence of a small-scale magnetic loop in the internetwork followed
soon afterwards by a campfire brightening adjacent to the location
of the linear polarisation signal in the photosphere, that is to
say near where the apex of the emerging loop lays. The rest of the
events were observed over small scattered magnetic features, which
could not be identified as magnetic footpoints of the campfire hosting
loops. <BR /> Conclusions: The majority of campfires could be driven
by magnetic reconnection triggered at the footpoints, similar to the
physical processes occurring in the burst-like EUV events discussed
in the literature. About a quarter of all analysed campfires, however,
are not associated to such magnetic activity in the photosphere, which
implies that other heating mechanisms are energising these small-scale
EUV brightenings.
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Title: PLATO Performance
Authors: Cabrera, J.; Rauer, H.; Börner, A.; Grießbach, D.; Paproth,
C.; Samadi, R.; Appourchaux, T.
2021plat.confE..95C Altcode:
The PLATO mission (PLAnetary Transits and Oscillations of stars,
hereafter abbreviated as PLATO) has been selected as part of ESA's
Cosmic Vision 2015-2025 program for the M3 mission launch foreseen
in 2026. The main science goal of PLATO is to detect and characterize
extrasolar planets, including terrestrial planets in the habitable zone
(HZ) of their host stars. Characterization here means to derive accurate
planetary radii, masses, and ages. In order to achieve these goals,
it is mandatory to characterize the host stars. As transit search
is an indirect detection and characterization method, the accurate
knowledge of the host star parameters limits the accuracy of the derived
planet parameters. PLATO will therefore monitor hundreds of thousands
of stars for up to three years in order to fully characterize stars
with asteroseismology and to detect transiting planets. The resulting
large data set of stellar light curves provides an additional science
return of the mission that reaches far beyond the exoplanet science
case into stellar, Galactic, and extragalactic research. <P />PLATO
Payload features a multi-telescope configuration consisting of 26
cameras, of 12 cm pupil size aperture each, covering a field of view of
about 2000 square degrees spread over 104 CCDs of 20 million pixels a
piece. PLATO has strict noise requirements achieved through excellent
optics transmission and quantum efficiency, low read-out noise, and
stringent pointing requirements. <P />In this talk we will review the
drivers for PLATO Performance and present the most recent description
of the status of noise budget and verification of main performance
requirements (including field of view and pointing performance).
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Title: A journey of exploration to the polar regions of a star:
probing the solar poles and the heliosphere from high helio-latitude
Authors: Harra, Louise; Andretta, Vincenzo; Appourchaux, Thierry;
Baudin, Frédéric; Bellot-Rubio, Luis; Birch, Aaron C.; Boumier,
Patrick; Cameron, Robert H.; Carlsson, Matts; Corbard, Thierry;
Davies, Jackie; Fazakerley, Andrew; Fineschi, Silvano; Finsterle,
Wolfgang; Gizon, Laurent; Harrison, Richard; Hassler, Donald M.;
Leibacher, John; Liewer, Paulett; Macdonald, Malcolm; Maksimovic,
Milan; Murphy, Neil; Naletto, Giampiero; Nigro, Giuseppina; Owen,
Christopher; Martínez-Pillet, Valentín; Rochus, Pierre; Romoli,
Marco; Sekii, Takashi; Spadaro, Daniele; Veronig, Astrid; Schmutz, W.
2021ExA...tmp...93H Altcode: 2021arXiv210410876H
A mission to view the solar poles from high helio-latitudes (above 60°)
will build on the experience of Solar Orbiter as well as a long heritage
of successful solar missions and instrumentation (e.g. SOHO Domingo et
al. (Solar Phys. 162(1-2), 1-37 1995), STEREO Howard et al. (Space
Sci. Rev. 136(1-4), 67-115 2008), Hinode Kosugi et al. (Solar
Phys. 243(1), 3-17 2007), Pesnell et al. Solar Phys. 275(1-2),
3-15 2012), but will focus for the first time on the solar poles,
enabling scientific investigations that cannot be done by any other
mission. One of the major mysteries of the Sun is the solar cycle. The
activity cycle of the Sun drives the structure and behaviour of the
heliosphere and of course, the driver of space weather. In addition,
solar activity and variability provides fluctuating input into the
Earth climate models, and these same physical processes are applicable
to stellar systems hosting exoplanets. One of the main obstructions
to understanding the solar cycle, and hence all solar activity,
is our current lack of understanding of the polar regions. In this
White Paper, submitted to the European Space Agency in response to the
Voyage 2050 call, we describe a mission concept that aims to address
this fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.
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Title: Amplitude of solar gravity modes generated by penetrative
plumes
Authors: Pinçon, C.; Appourchaux, T.; Buldgen, G.
2021A&A...650A..47P Altcode: 2021arXiv210303760P
Context. The observation of gravity modes is expected to give us
unprecedented insights into the inner dynamics of the Sun. Nevertheless,
there is currently no consensus on their detection. Within this
framework, predicting their amplitudes is essential to guide future
observational strategies and seismic studies. <BR /> Aims: While
previous estimates considered convective turbulent eddies as the
driving mechanism, our aim is to predict the amplitude of low-frequency
asymptotic gravity modes generated by penetrative convection at the top
of the radiative zone. <BR /> Methods: A generation model previously
developed for progressive gravity waves was adapted to the case of
resonant gravity modes. The stellar oscillation equations were analyzed
considering the plume ram pressure at the top of the radiative zone as
the forcing term. The plume velocity field was modeled in an analytical
form. <BR /> Results: We obtain an analytical expression for the mode
energy. It is found to depend critically on the time evolution of the
plumes inside the generation region. Using a solar model, we then
compute the apparent surface radial velocity of low-degree gravity
modes as would be measured by the GOLF instrument, in the frequency
range 10 µHz ≤ ν ≤ 100 µHz. In the case of a Gaussian plume
time evolution, gravity modes turn out to be undetectable because of
too small surface amplitudes. This holds true despite a wide range
of values considered for the parameters of the model. In the other
limiting case of an exponential time evolution, plumes are expected
to drive gravity modes in a much more efficient way because of a much
higher temporal coupling between the plumes and the modes than in the
Gaussian case. Using reasonable values for the plume parameters based
on semi-analytical models, the apparent surface velocities in this
case are one order of magnitude lower than the 22-year GOLF detection
threshold and lower than the previous estimates considering turbulent
pressure as the driving mechanism, with a maximum value of 0.05 cm
s<SUP>−1</SUP> for ℓ = 1 and ν ≈ 100 µHz. When accounting
for uncertainties on the plume parameters, the apparent surface
velocities in the most favorable plausible case become comparable to
those predicted with turbulent pressure, and the GOLF observation time
required for a detection at ν ≈ 100 µHz and ℓ = 1 is reduced
to about 50 yr. <BR /> Conclusions: Penetrative convection can drive
gravity modes in the most favorable plausible case as efficiently
as turbulent pressure, with amplitudes slightly below the current
detection threshold. When detected in the future, the measurement
of their amplitudes is expected to provide information on the plume
dynamics at the base of the convective zone. In order to make a proper
interpretation, this potential nevertheless requires further theoretical
improvements in our description of penetrative plumes.
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Title: Characteristics and performances of an interferometric Doppler
imager installed at the 188 cm telescope of Okayama Observatory
Authors: Schmider, François-Xavier; Dejonghe, Julien; Guillot,
Tristan; Ikoma, Masahiro; Boumier, Patrick; Sato, Bun'ei; Jackiewicz,
Jason; Izumiura, Hideyuki; Hanayama, Hidekazu; Abe, Lyu; Gonçalves,
Ivan; Gouvret, Carole; Fantéï-Caujolle, Yan; Morand, Frédéric;
Preis, Olivier; Rivet, Jean-Pierre; Appourchaux, Thierry; Leclec'h,
Jean-Christophe; Ballans, Hervé; Langlet, François; Baudin,
Frédéric; Aoyama, Yuhiko; Kawaushi, Kiyoe; Horiuchi, Takashi;
Gaulme, Patrick; Voelz, David; Underwood, Thomas
2020SPIE11447E..3DS Altcode:
We describe the performances of a novel Doppler imager, aimed to
detect acoustic oscillations and atmospheric dynamics at the surface of
giant planets of the Solar System in the frame of the JOVIAL (Jovian
Oscillations detection by Velocity Imaging At several Longitudes)
project. The first JOVIAL instrument was installed on the 188cm
telescope at Okayama branch of National Astronomical Observatory of
Japan (NAOJ) in April 2019. This instrument is a part of a ground based
network of three identical instruments installed on telescopes around
the world for continuous observations. First observations of Jupiter
with the JOVIAL instrument were achieved in June 2019. We describe the
instrument principle, its design and the set-up at Okayama observatory,
as well as the performances reached during the first observing run. We
finally provide plans for future observations with the network.
---------------------------------------------------------
Title: A Journey of Exploration to the Polar Regions of a Star:
Probing the Solar Poles and the Heliosphere from High Helio-Latitude
Authors: Finsterle, W.; Harra, L.; Andretta, V.; Appourchaux, T.;
Baudin, F.; Bellot Rubio, L.; Birch, A.; Boumier, P.; Cameron, R. H.;
Carlsson, M.; Corbard, T.; Davies, J. A.; Fazakerley, A. N.; Fineschi,
S.; Gizon, L. C.; Harrison, R. A.; Hassler, D.; Leibacher, J. W.;
Liewer, P. C.; Macdonald, M.; Maksimovic, M.; Murphy, N.; Naletto, G.;
Nigro, G.; Owen, C. J.; Martinez-Pillet, V.; Rochus, P. L.; Romoli,
M.; Sekii, T.; Spadaro, D.; Veronig, A.
2020AGUFMSH0110005F Altcode:
A mission to view the solar poles from high helio-latitudes (above
60°) will build on the experience of Solar Orbiter as well as a long
heritage of successful solar missions and instrumentation (e.g. SOHO,
STEREO, Hinode, SDO), but will focus for the first time on the solar
poles, enabling scientific investigations that cannot be done by
any other mission. One of the major mysteries of the Sun is the solar
cycle. The activity cycle of the Sun drives the structure and behaviour
of the heliosphere and is, of course, the driver of space weather. In
addition, solar activity and variability provides fluctuating input
into the Earth climate models, and these same physical processes
are applicable to stellar systems hosting exoplanets. One of the
main obstructions to understanding the solar cycle, and hence all
solar activity, is our current lack of understanding of the polar
regions. We describe a mission concept that aims to address this
fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.
---------------------------------------------------------
Title: The Solar Orbiter Science Activity Plan. Translating solar
and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
T.; Young, P. R.; Zhukov, A. N.
2020A&A...642A...3Z Altcode: 2020arXiv200910772Z
Solar Orbiter is the first space mission observing the solar plasma
both in situ and remotely, from a close distance, in and out of the
ecliptic. The ultimate goal is to understand how the Sun produces
and controls the heliosphere, filling the Solar System and driving
the planetary environments. With six remote-sensing and four in-situ
instrument suites, the coordination and planning of the operations are
essential to address the following four top-level science questions:
(1) What drives the solar wind and where does the coronal magnetic field
originate?; (2) How do solar transients drive heliospheric variability?;
(3) How do solar eruptions produce energetic particle radiation that
fills the heliosphere?; (4) How does the solar dynamo work and drive
connections between the Sun and the heliosphere? Maximising the
mission's science return requires considering the characteristics
of each orbit, including the relative position of the spacecraft
to Earth (affecting downlink rates), trajectory events (such
as gravitational assist manoeuvres), and the phase of the solar
activity cycle. Furthermore, since each orbit's science telemetry
will be downloaded over the course of the following orbit, science
operations must be planned at mission level, rather than at the level
of individual orbits. It is important to explore the way in which those
science questions are translated into an actual plan of observations
that fits into the mission, thus ensuring that no opportunities are
missed. First, the overarching goals are broken down into specific,
answerable questions along with the required observations and the
so-called Science Activity Plan (SAP) is developed to achieve this. The
SAP groups objectives that require similar observations into Solar
Orbiter Observing Plans, resulting in a strategic, top-level view of
the optimal opportunities for science observations during the mission
lifetime. This allows for all four mission goals to be addressed. In
this paper, we introduce Solar Orbiter's SAP through a series of
examples and the strategy being followed.
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Title: The Polarimetric and Helioseismic Imager on Solar Orbiter
Authors: Solanki, S. K.; del Toro Iniesta, J. C.; Woch, J.; Gandorfer,
A.; Hirzberger, J.; Alvarez-Herrero, A.; Appourchaux, T.; Martínez
Pillet, V.; Pérez-Grande, I.; Sanchis Kilders, E.; Schmidt, W.;
Gómez Cama, J. M.; Michalik, H.; Deutsch, W.; Fernandez-Rico, G.;
Grauf, B.; Gizon, L.; Heerlein, K.; Kolleck, M.; Lagg, A.; Meller, R.;
Müller, R.; Schühle, U.; Staub, J.; Albert, K.; Alvarez Copano, M.;
Beckmann, U.; Bischoff, J.; Busse, D.; Enge, R.; Frahm, S.; Germerott,
D.; Guerrero, L.; Löptien, B.; Meierdierks, T.; Oberdorfer, D.;
Papagiannaki, I.; Ramanath, S.; Schou, J.; Werner, S.; Yang, D.;
Zerr, A.; Bergmann, M.; Bochmann, J.; Heinrichs, J.; Meyer, S.;
Monecke, M.; Müller, M. -F.; Sperling, M.; Álvarez García, D.;
Aparicio, B.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Cobos
Carracosa, J. P.; Girela, F.; Hernández Expósito, D.; Herranz, M.;
Labrousse, P.; López Jiménez, A.; Orozco Suárez, D.; Ramos, J. L.;
Barandiarán, J.; Bastide, L.; Campuzano, C.; Cebollero, M.; Dávila,
B.; Fernández-Medina, A.; García Parejo, P.; Garranzo-García, D.;
Laguna, H.; Martín, J. A.; Navarro, R.; Núñez Peral, A.; Royo, M.;
Sánchez, A.; Silva-López, M.; Vera, I.; Villanueva, J.; Fourmond,
J. -J.; de Galarreta, C. Ruiz; Bouzit, M.; Hervier, V.; Le Clec'h,
J. C.; Szwec, N.; Chaigneau, M.; Buttice, V.; Dominguez-Tagle, C.;
Philippon, A.; Boumier, P.; Le Cocguen, R.; Baranjuk, G.; Bell,
A.; Berkefeld, Th.; Baumgartner, J.; Heidecke, F.; Maue, T.; Nakai,
E.; Scheiffelen, T.; Sigwarth, M.; Soltau, D.; Volkmer, R.; Blanco
Rodríguez, J.; Domingo, V.; Ferreres Sabater, A.; Gasent Blesa,
J. L.; Rodríguez Martínez, P.; Osorno Caudel, D.; Bosch, J.; Casas,
A.; Carmona, M.; Herms, A.; Roma, D.; Alonso, G.; Gómez-Sanjuan, A.;
Piqueras, J.; Torralbo, I.; Fiethe, B.; Guan, Y.; Lange, T.; Michel,
H.; Bonet, J. A.; Fahmy, S.; Müller, D.; Zouganelis, I.
2020A&A...642A..11S Altcode: 2019arXiv190311061S
<BR /> Aims: This paper describes the Polarimetric and Helioseismic
Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and
helioseismology instrument to observe the Sun from outside the Sun-Earth
line. It is the key instrument meant to address the top-level science
question: How does the solar dynamo work and drive connections between
the Sun and the heliosphere? SO/PHI will also play an important role
in answering the other top-level science questions of Solar Orbiter,
while hosting the potential of a rich return in further science. <BR
/> Methods: SO/PHI measures the Zeeman effect and the Doppler shift
in the Fe I 617.3 nm spectral line. To this end, the instrument
carries out narrow-band imaging spectro-polarimetry using a tunable
LiNbO<SUB>3</SUB> Fabry-Perot etalon, while the polarisation modulation
is done with liquid crystal variable retarders. The line and the nearby
continuum are sampled at six wavelength points and the data are recorded
by a 2k × 2k CMOS detector. To save valuable telemetry, the raw data
are reduced on board, including being inverted under the assumption of
a Milne-Eddington atmosphere, although simpler reduction methods are
also available on board. SO/PHI is composed of two telescopes; one,
the Full Disc Telescope, covers the full solar disc at all phases of
the orbit, while the other, the High Resolution Telescope, can resolve
structures as small as 200 km on the Sun at closest perihelion. The high
heat load generated through proximity to the Sun is greatly reduced by
the multilayer-coated entrance windows to the two telescopes that allow
less than 4% of the total sunlight to enter the instrument, most of
it in a narrow wavelength band around the chosen spectral line. <BR />
Results: SO/PHI was designed and built by a consortium having partners
in Germany, Spain, and France. The flight model was delivered to
Airbus Defence and Space, Stevenage, and successfully integrated into
the Solar Orbiter spacecraft. A number of innovations were introduced
compared with earlier space-based spectropolarimeters, thus allowing
SO/PHI to fit into the tight mass, volume, power and telemetry budgets
provided by the Solar Orbiter spacecraft and to meet the (e.g. thermal)
challenges posed by the mission's highly elliptical orbit.
---------------------------------------------------------
Title: The Solar Orbiter SPICE instrument. An extreme UV imaging
spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
2020A&A...642A..14S Altcode: 2019arXiv190901183A; 2019arXiv190901183S
<BR /> Aims: The Spectral Imaging of the Coronal Environment (SPICE)
instrument is a high-resolution imaging spectrometer operating at
extreme ultraviolet wavelengths. In this paper, we present the concept,
design, and pre-launch performance of this facility instrument on the
ESA/NASA Solar Orbiter mission. <BR /> Methods: The goal of this paper
is to give prospective users a better understanding of the possible
types of observations, the data acquisition, and the sources that
contribute to the instrument's signal. <BR /> Results: The paper
discusses the science objectives, with a focus on the SPICE-specific
aspects, before presenting the instrument's design, including optical,
mechanical, thermal, and electronics aspects. This is followed by a
characterisation and calibration of the instrument's performance. The
paper concludes with descriptions of the operations concept and data
processing. <BR /> Conclusions: The performance measurements of the
various instrument parameters meet the requirements derived from the
mission's science objectives. The SPICE instrument is ready to perform
measurements that will provide vital contributions to the scientific
success of the Solar Orbiter mission.
---------------------------------------------------------
Title: On attempting to automate the identification of mixed dipole
modes for subgiant stars
Authors: Appourchaux, T.
2020A&A...642A.226A Altcode: 2020arXiv200810973A
Context. The existence of mixed modes in stars is a marker of stellar
evolution. Their detection serves for a better determination of
stellar age. <BR /> Aims: The goal of this paper is to identify the
dipole modes in an automatic manner without human intervention. <BR
/> Methods: I used the power spectra obtained by the Kepler mission
for the application of the method. I computed asymptotic dipole mode
frequencies as a function of the coupling factor and dipole period
spacing, as well as other parameters. For each star, I collapsed the
power in an echelle diagramme aligned onto the monopole and dipole
mixed modes. The power at the null frequency was used as a figure
of merit. Using a genetic algorithm, I then optimised the figure of
merit by adjusting the location of the dipole frequencies in the power
spectrum. Using published frequencies, I compared the asymptotic dipole
mode frequencies with published frequencies. I also used published
frequencies to derive the coupling factor and dipole period spacing
using a non-linear least squares fit. I used Monte-Carlo simulations
of the non-linear least square fit to derive error bars for each
parameter. <BR /> Results: From the 44 subgiants studied, the automatic
identification allows one to retrieve within 3 μHz, at least 80% of
the modes for 32 stars, and within 6 μHz, at least 90% of the modes
for 37 stars. The optimised and fitted gravity-mode period spacing and
coupling factor are in agreement with previous measurements. Random
errors for the mixed-mode parameters deduced from the Monte-Carlo
simulation are about 30-50 times smaller than previously determined
errors, which are in fact systematic errors. <BR /> Conclusions: The
period spacing and coupling factors of mixed modes in subgiants are
confirmed. The current automated procedure will need to be improved upon
using a more accurate asymptotic model and/or proper statistical tests.
---------------------------------------------------------
Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
Imager
Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz,
W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado,
R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.;
Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel,
V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau,
M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar,
S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.;
Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.;
Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.;
Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud,
A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.;
Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.;
Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan,
K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.;
Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.;
Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq,
S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.;
Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining,
S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort,
F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.;
Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.;
Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.;
Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.;
Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane,
K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit,
S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen,
K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.;
Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.;
Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.;
Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N.
2020A&A...642A...8R Altcode:
Context. The Extreme Ultraviolet Imager (EUI) is part of the remote
sensing instrument package of the ESA/NASA Solar Orbiter mission
that will explore the inner heliosphere and observe the Sun from
vantage points close to the Sun and out of the ecliptic. Solar Orbiter
will advance the "connection science" between solar activity and the
heliosphere. <BR /> Aims: With EUI we aim to improve our understanding
of the structure and dynamics of the solar atmosphere, globally as well
as at high resolution, and from high solar latitude perspectives. <BR />
Methods: The EUI consists of three telescopes, the Full Sun Imager and
two High Resolution Imagers, which are optimised to image in Lyman-α
and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere
up to corona. The EUI is designed to cope with the strong constraints
imposed by the Solar Orbiter mission characteristics. Limited telemetry
availability is compensated by state-of-the-art image compression,
onboard image processing, and event selection. The imposed power
limitations and potentially harsh radiation environment necessitate
the use of novel CMOS sensors. As the unobstructed field of view of
the telescopes needs to protrude through the spacecraft's heat shield,
the apertures have been kept as small as possible, without compromising
optical performance. This led to a systematic effort to optimise the
throughput of every optical element and the reduction of noise levels
in the sensor. <BR /> Results: In this paper we review the design
of the two elements of the EUI instrument: the Optical Bench System
and the Common Electronic Box. Particular attention is also given to
the onboard software, the intended operations, the ground software,
and the foreseen data products. <BR /> Conclusions: The EUI will
bring unique science opportunities thanks to its specific design,
its viewpoint, and to the planned synergies with the other Solar
Orbiter instruments. In particular, we highlight science opportunities
brought by the out-of-ecliptic vantage point of the solar poles,
the high-resolution imaging of the high chromosphere and corona,
and the connection to the outer corona as observed by coronagraphs.
---------------------------------------------------------
Title: The Evolution of Rotation and Magnetic Activity in 94 Aqr Aa
from Asteroseismology with TESS
Authors: Metcalfe, Travis S.; van Saders, Jennifer L.; Basu, Sarbani;
Buzasi, Derek; Chaplin, William J.; Egeland, Ricky; Garcia, Rafael
A.; Gaulme, Patrick; Huber, Daniel; Reinhold, Timo; Schunker, Hannah;
Stassun, Keivan G.; Appourchaux, Thierry; Ball, Warrick H.; Bedding,
Timothy R.; Deheuvels, Sébastien; González-Cuesta, Lucía; Handberg,
Rasmus; Jiménez, Antonio; Kjeldsen, Hans; Li, Tanda; Lund, Mikkel N.;
Mathur, Savita; Mosser, Benoit; Nielsen, Martin B.; Noll, Anthony;
Çelik Orhan, Zeynep; Örtel, Sibel; Santos, Ângela R. G.; Yildiz,
Mutlu; Baliunas, Sallie; Soon, Willie
2020ApJ...900..154M Altcode: 2020arXiv200712755M
Most previous efforts to calibrate how rotation and magnetic activity
depend on stellar age and mass have relied on observations of clusters,
where isochrones from stellar evolution models are used to determine the
properties of the ensemble. Asteroseismology employs similar models to
measure the properties of an individual star by matching its normal
modes of oscillation, yielding the stellar age and mass with high
precision. We use 27 days of photometry from the Transiting Exoplanet
Survey Satellite to characterize solar-like oscillations in the G8
subgiant of the 94 Aqr triple system. The resulting stellar properties,
when combined with a reanalysis of 35 yr of activity measurements
from the Mount Wilson HK project, allow us to probe the evolution of
rotation and magnetic activity in the system. The asteroseismic age
of the subgiant agrees with a stellar isochrone fit, but the rotation
period is much shorter than expected from standard models of angular
momentum evolution. We conclude that weakened magnetic braking may be
needed to reproduce the stellar properties, and that evolved subgiants
in the hydrogen shell-burning phase can reinvigorate large-scale dynamo
action and briefly sustain magnetic activity cycles before ascending
the red giant branch.
---------------------------------------------------------
Title: The Solaris Solar Polar Mission
Authors: Hassler, Donald M.; Newmark, Jeff; Gibson, Sarah; Harra,
Louise; Appourchaux, Thierry; Auchere, Frederic; Berghmans, David;
Colaninno, Robin; Fineschi, Silvano; Gizon, Laurent; Gosain, Sanjay;
Hoeksema, Todd; Kintziger, Christian; Linker, John; Rochus, Pierre;
Schou, Jesper; Viall, Nicholeen; West, Matt; Woods, Tom; Wuelser,
Jean-Pierre
2020EGUGA..2217703H Altcode:
The solar poles are one of the last unexplored regions of the solar
system. Although Ulysses flew over the poles in the 1990s, it did
not have remote sensing instruments onboard to probe the Sun's polar
magnetic field or surface/sub-surface flows.We will discuss Solaris,
a proposed Solar Polar MIDEX mission to revolutionize our understanding
of the Sun by addressing fundamental questions that can only be answered
from a polar vantage point. Solaris uses a Jupiter gravity assist to
escape the ecliptic plane and fly over both poles of the Sun to >75
deg. inclination, obtaining the first high-latitude, multi-month-long,
continuous remote-sensing solar observations. Solaris will address key
outstanding, breakthrough problems in solar physics and fill holes in
our scientific understanding that will not be addressed by current
missions.With focused science and a simple, elegant mission design,
Solaris will also provide enabling observations for space weather
research (e.g. polar view of CMEs), and stimulate future research
through new unanticipated discoveries.
---------------------------------------------------------
Title: Age dating of an early Milky Way merger via asteroseismology
of the naked-eye star ν Indi
Authors: Chaplin, William J.; Serenelli, Aldo M.; Miglio, Andrea;
Morel, Thierry; Mackereth, J. Ted; Vincenzo, Fiorenzo; Kjeldsen, Hans;
Basu, Sarbani; Ball, Warrick H.; Stokholm, Amalie; Verma, Kuldeep;
Mosumgaard, Jakob Rørsted; Silva Aguirre, Victor; Mazumdar, Anwesh;
Ranadive, Pritesh; Antia, H. M.; Lebreton, Yveline; Ong, Joel;
Appourchaux, Thierry; Bedding, Timothy R.; Christensen-Dalsgaard,
Jørgen; Creevey, Orlagh; García, Rafael A.; Handberg, Rasmus; Huber,
Daniel; Kawaler, Steven D.; Lund, Mikkel N.; Metcalfe, Travis S.;
Stassun, Keivan G.; Bazot, Michäel; Beck, Paul G.; Bell, Keaton J.;
Bergemann, Maria; Buzasi, Derek L.; Benomar, Othman; Bossini, Diego;
Bugnet, Lisa; Campante, Tiago L.; Orhan, Zeynep çelik; Corsaro,
Enrico; González-Cuesta, Lucía; Davies, Guy R.; Di Mauro, Maria
Pia; Egeland, Ricky; Elsworth, Yvonne P.; Gaulme, Patrick; Ghasemi,
Hamed; Guo, Zhao; Hall, Oliver J.; Hasanzadeh, Amir; Hekker, Saskia;
Howe, Rachel; Jenkins, Jon M.; Jiménez, Antonio; Kiefer, René;
Kuszlewicz, James S.; Kallinger, Thomas; Latham, David W.; Lundkvist,
Mia S.; Mathur, Savita; Montalbán, Josefina; Mosser, Benoit; Bedón,
Andres Moya; Nielsen, Martin Bo; Örtel, Sibel; Rendle, Ben M.; Ricker,
George R.; Rodrigues, Thaíse S.; Roxburgh, Ian W.; Safari, Hossein;
Schofield, Mathew; Seager, Sara; Smalley, Barry; Stello, Dennis;
Szabó, Róbert; Tayar, Jamie; Themeßl, Nathalie; Thomas, Alexandra
E. L.; Vanderspek, Roland K.; van Rossem, Walter E.; Vrard, Mathieu;
Weiss, Achim; White, Timothy R.; Winn, Joshua N.; Yıldız, Mutlu
2020NatAs...4..382C Altcode: 2020NatAs.tmp....7C; 2020arXiv200104653C
Over the course of its history, the Milky Way has ingested multiple
smaller satellite galaxies<SUP>1</SUP>. Although these accreted
stellar populations can be forensically identified as kinematically
distinct structures within the Galaxy, it is difficult in general
to date precisely the age at which any one merger occurred. Recent
results have revealed a population of stars that were accreted via the
collision of a dwarf galaxy, called Gaia-Enceladus<SUP>1</SUP>, leading
to substantial pollution of the chemical and dynamical properties of
the Milky Way. Here we identify the very bright, naked-eye star ν
Indi as an indicator of the age of the early in situ population of
the Galaxy. We combine asteroseismic, spectroscopic, astrometric and
kinematic observations to show that this metal-poor, alpha-element-rich
star was an indigenous member of the halo, and we measure its age
to be 11.0 ±0.7 ? (stat) ±0.8 ? (sys) billion years. The star
bears hallmarks consistent with having been kinematically heated by
the Gaia-Enceladus collision. Its age implies that the earliest the
merger could have begun was 11.6 and 13.2 billion years ago, at 68%
and 95% confidence, respectively. Computations based on hierarchical
cosmological models slightly reduce the above limits.
---------------------------------------------------------
Title: Jupiter atmospheric dynamics from ground-based Doppler imaging
Authors: Schmider, François-Xavier; Guillot, Tristan; Gonçalves,
Ivan; Jackiewicz, Jason; Underwood, Thomas; Voelz, David; Gaulme,
Patrick; Boumier, Patrick; Appourchaux, Thierry; Morales-Juberias,
Raùl; Ikoma, Masahiro; Sato, Bun'ei; Izumiura, Hideyuki
2019EPSC...13.1613S Altcode:
We present velocity maps of Jupiter obtained from the ground with a
dedicated Doppler imaging spectrograph. It demonstrates the potential
of this method to study the motion in the atmosphere of gaseous
planets. It proves to be complementary to cloud-tracking to understand
the atmospheric dynamics
---------------------------------------------------------
Title: VizieR Online Data Catalog: High-precision radial velocities
for HD 221416 (Huber+, 2019)
Authors: Huber, D.; Chaplin, W. J.; Chontos, A.; Kjeldsen, H.;
Christensen-Dalsgaard, J.; Bedding, T. R.; Ball, W.; Brahm, R.;
Espinoza, N.; Henning, T.; Jordan, A.; Sarkis, P.; Knudstrup, E.;
Albrecht, S.; Grundahl, F.; Andersen, M. F.; Palle, P. L.; Crossfield,
I.; Fulton, B.; Howard, A. W.; Isaacson, H. T.; Weiss, L. M.; Handberg,
R.; Lund, M. N.; Serenelli, A. M.; Rorsted Mosumgaard, J.; Stokholm,
A.; Bieryla, A.; Buchhave, L. A.; Latham, D. W.; Quinn, S. N.;
Gaidos, E.; Hirano, T.; Ricker, G. R.; Vanderspek, R. K.; Seager,
S.; Jenkins, J. M.; Winn, J. N.; Antia, H. M.; Appourchaux, T.; Basu,
S.; Bell, K. J.; Benomar, O.; Bonanno, A.; Buzasi, D. L.; Campante,
T. L.; Celik Orhan, Z.; Corsaro, E.; Cunha, M. S.; Davies, G. R.;
Deheuvels, S.; Grunblatt, S. K.; Hasanzadeh, A.; di Mauro, M. P.;
Garcia, R. A.; Gaulme, P.; Girardi, L.; Guzik, J. A.; Hon, M.; Jiang,
C.; Kallinger, T.; Kawaler, S. D.; Kuszlewicz, J. S.; Lebreton, Y.; Li,
T.; Lucas, M.; Lundkvist, M. S.; Mann, A. W.; Mathis, S.; Mathur, S.;
Mazumdar, A.; Metcalfe, T. S.; Miglio, A.; Monteiro, M. J. P. F. G.;
Mosser, B.; Noll, A.; Nsamba, B.; Ong, J. M. J.; Ortel, S.; Pereira,
F.; Ranadive, P.; Regulo, C.; Rodrigues, T. S.; Roxburgh, I. W.;
Aguirre, V. S.; Smalley, B.; Schofield, M.; Sousa, S. G.; Stassun,
K. G.; Stello, D.; Tayar, J.; White, T. R.; Verma, K.; Vrard, M.;
Yildiz, M.; Baker, D.; Bazot, M.; Beichmann, C.; Bergmann, C.;
Bugnet, L.; Cale, B.; Carlino, R.; Cartwright, S. M.; Christiansen,
J. L.; Ciardi, D. R.; Creevey, O.; Dittmann, J. A.; Do Nascimento,
J. -D., Jr.; van Eylen, V.; Furesz, G.; Gagne, J.; Gao, P.; Gazeas,
K.; Giddens, F.; Hall, O. J.; Hekker, S.; Ireland, M. J.; Latouf,
N.; Lebrun, D.; Levine, A. M.; Matzko, W.; Natinsky, E.; Page, E.;
Plavchan, P.; Mansouri-Samani, M.; McCauliff, S.; Mullally, S. E.;
Orenstein, B.; Soto, A. G.; Paegert, M.; van Saders, J. L.; Schnaible,
C.; Soderblom, D. R.; Szabo, R.; Tanner, A.; Tinney, C. G.; Teske,
J.; Thomas, A.; Trampedach, R.; Wright, D.; Yuan, T. T.; Zohrabi, F.
2019yCat..51570245H Altcode:
We obtained high-resolution spectra of HD 221416 using several
facilities within the TESS Follow-up Observation Program (TFOP),
including HIRES (Vogt et al. 1994SPIE.2198..362V) on the 10 m telescope
at Keck Observatory (Maunakea, Hawai'i); the Hertzsprung SONG Telescope
at Teide Observatory (Tenerife; Grundahl et al. 2017ApJ...836..142G);
HARPS (Mayor et al. 2003Msngr.114...20M), FEROS (Kaufer et
al. 1999Msngr..95....8K), Coralie (Queloz et al. 2001Msngr.105....1Q),
and FIDEOS (Vanzi et al. 2018MNRAS.477.5041V) on the MPG/ESO 3.6 m, 2.2
m, 1.2 m, and 1 m telescopes at La Silla Observatory (Chile); Veloce
(Gilbert et al. 2018SPIE10702E..0YG) on the 3.9 m Anglo-Australian
Telescope at Siding Spring Observatory (Australia); TRES (Furesz 2008,
PhD thesis Univ. Szeged) on the 1.5 m Tillinghast reflector at the
F. L. Whipple Observatory (Mt. Hopkins, Arizona); and iSHELL (Rayner
et al. 2012SPIE.8446E..2CR) on the NASA IRTF Telescope (Maunakea,
Hawai'i). All spectra used in this paper were obtained between 2018
November 11 and December 30 and have a minimum spectral resolution of
R~44000. <P />(1 data file).
---------------------------------------------------------
Title: Damping rates and frequency corrections of Kepler LEGACY stars
Authors: Houdek, G.; Lund, M. N.; Trampedach, R.;
Christensen-Dalsgaard, J.; Handberg, R.; Appourchaux, T.
2019MNRAS.487..595H Altcode: 2019MNRAS.tmp.1157H; 2019arXiv190413170H
Linear damping rates and modal frequency corrections of radial
oscillation modes in selected LEGACY main-sequence stars are
estimated by means of a non-adiabatic stability analysis. The
selected stellar sample covers stars observed by Kepler with a large
range of surface temperatures and surface gravities. A non-local,
time-dependent convection model is perturbed to assess stability
against pulsation modes. The mixing-length parameter is calibrated
to the surface-convection-zone depth of a stellar model obtained from
fitting adiabatic frequencies to the LEGACY observations, and two of
the non-local convection parameters are calibrated to the corresponding
LEGACY linewidth measurements. The remaining non-local convection
parameters in the 1D calculations are calibrated so as to reproduce
profiles of turbulent pressure and of the anisotropy of the turbulent
velocity field of corresponding 3D hydrodynamical simulations. The
atmospheric structure in the 1D stability analysis adopts a
temperature-optical-depth relation derived from 3D hydrodynamical
simulations. Despite the small number of parameters to adjust, we
find good agreement with detailed shapes of both turbulent pressure
profiles and anisotropy profiles with depth, and with damping rates
as a function of frequency. Furthermore, we find the absolute modal
frequency corrections, relative to a standard adiabatic pulsation
calculation, to increase with surface temperature and surface gravity.
---------------------------------------------------------
Title: A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered
by TESS
Authors: Huber, Daniel; Chaplin, William J.; Chontos, Ashley; Kjeldsen,
Hans; Christensen-Dalsgaard, Jørgen; Bedding, Timothy R.; Ball,
Warrick; Brahm, Rafael; Espinoza, Nestor; Henning, Thomas; Jordán,
Andrés; Sarkis, Paula; Knudstrup, Emil; Albrecht, Simon; Grundahl,
Frank; Fredslund Andersen, Mads; Pallé, Pere L.; Crossfield, Ian;
Fulton, Benjamin; Howard, Andrew W.; Isaacson, Howard T.; Weiss,
Lauren M.; Handberg, Rasmus; Lund, Mikkel N.; Serenelli, Aldo M.;
Rørsted Mosumgaard, Jakob; Stokholm, Amalie; Bieryla, Allyson;
Buchhave, Lars A.; Latham, David W.; Quinn, Samuel N.; Gaidos, Eric;
Hirano, Teruyuki; Ricker, George R.; Vanderspek, Roland K.; Seager,
Sara; Jenkins, Jon M.; Winn, Joshua N.; Antia, H. M.; Appourchaux,
Thierry; Basu, Sarbani; Bell, Keaton J.; Benomar, Othman; Bonanno,
Alfio; Buzasi, Derek L.; Campante, Tiago L.; Çelik Orhan, Z.; Corsaro,
Enrico; Cunha, Margarida S.; Davies, Guy R.; Deheuvels, Sebastien;
Grunblatt, Samuel K.; Hasanzadeh, Amir; Di Mauro, Maria Pia; García,
Rafael A.; Gaulme, Patrick; Girardi, Léo; Guzik, Joyce A.; Hon, Marc;
Jiang, Chen; Kallinger, Thomas; Kawaler, Steven D.; Kuszlewicz, James
S.; Lebreton, Yveline; Li, Tanda; Lucas, Miles; Lundkvist, Mia S.;
Mann, Andrew W.; Mathis, Stéphane; Mathur, Savita; Mazumdar, Anwesh;
Metcalfe, Travis S.; Miglio, Andrea; Monteiro, Mário J. P. F. G.;
Mosser, Benoit; Noll, Anthony; Nsamba, Benard; Ong, Jia Mian Joel;
Örtel, S.; Pereira, Filipe; Ranadive, Pritesh; Régulo, Clara;
Rodrigues, Thaíse S.; Roxburgh, Ian W.; Silva Aguirre, Victor;
Smalley, Barry; Schofield, Mathew; Sousa, Sérgio G.; Stassun,
Keivan G.; Stello, Dennis; Tayar, Jamie; White, Timothy R.; Verma,
Kuldeep; Vrard, Mathieu; Yıldız, M.; Baker, David; Bazot, Michaël;
Beichmann, Charles; Bergmann, Christoph; Bugnet, Lisa; Cale, Bryson;
Carlino, Roberto; Cartwright, Scott M.; Christiansen, Jessie L.;
Ciardi, David R.; Creevey, Orlagh; Dittmann, Jason A.; Do Nascimento,
Jose-Dias, Jr.; Van Eylen, Vincent; Fürész, Gabor; Gagné, Jonathan;
Gao, Peter; Gazeas, Kosmas; Giddens, Frank; Hall, Oliver J.; Hekker,
Saskia; Ireland, Michael J.; Latouf, Natasha; LeBrun, Danny; Levine,
Alan M.; Matzko, William; Natinsky, Eva; Page, Emma; Plavchan,
Peter; Mansouri-Samani, Masoud; McCauliff, Sean; Mullally, Susan E.;
Orenstein, Brendan; Garcia Soto, Aylin; Paegert, Martin; van Saders,
Jennifer L.; Schnaible, Chloe; Soderblom, David R.; Szabó, Róbert;
Tanner, Angelle; Tinney, C. G.; Teske, Johanna; Thomas, Alexandra;
Trampedach, Regner; Wright, Duncan; Yuan, Thomas T.; Zohrabi, Farzaneh
2019AJ....157..245H Altcode: 2019arXiv190101643H
We present the discovery of HD 221416 b, the first transiting planet
identified by the Transiting Exoplanet Survey Satellite (TESS) for
which asteroseismology of the host star is possible. HD 221416 b
(HIP 116158, TOI-197) is a bright (V = 8.2 mag), spectroscopically
classified subgiant that oscillates with an average frequency of
about 430 μHz and displays a clear signature of mixed modes. The
oscillation amplitude confirms that the redder TESS bandpass compared
to Kepler has a small effect on the oscillations, supporting the
expected yield of thousands of solar-like oscillators with TESS 2
minute cadence observations. Asteroseismic modeling yields a robust
determination of the host star radius (R <SUB>⋆</SUB> = 2.943 ±
0.064 R <SUB>⊙</SUB>), mass (M <SUB>⋆</SUB> = 1.212 ± 0.074 M
<SUB>⊙</SUB>), and age (4.9 ± 1.1 Gyr), and demonstrates that it has
just started ascending the red-giant branch. Combining asteroseismology
with transit modeling and radial-velocity observations, we show that
the planet is a “hot Saturn” (R <SUB>p</SUB> = 9.17 ± 0.33 R
<SUB>⊕</SUB>) with an orbital period of ∼14.3 days, irradiance
of F = 343 ± 24 F <SUB>⊕</SUB>, and moderate mass (M <SUB>p</SUB>
= 60.5 ± 5.7 M <SUB>⊕</SUB>) and density (ρ <SUB>p</SUB> = 0.431
± 0.062 g cm<SUP>-3</SUP>). The properties of HD 221416 b show that
the host-star metallicity-planet mass correlation found in sub-Saturns
(4-8 R <SUB>⊕</SUB>) does not extend to larger radii, indicating that
planets in the transition between sub-Saturns and Jupiters follow a
relatively narrow range of densities. With a density measured to ∼15%,
HD 221416 b is one of the best characterized Saturn-size planets to
date, augmenting the small number of known transiting planets around
evolved stars and demonstrating the power of TESS to characterize
exoplanets and their host stars using asteroseismology.
---------------------------------------------------------
Title: Searching for g modes. II. Unconfirmed g-mode detection in
the power spectrum of the time series of round-trip travel time
Authors: Appourchaux, T.; Corbard, T.
2019A&A...624A.106A Altcode: 2019arXiv190303791A
Context. The recent claims of g-mode detection have restarted the search
for these potentially extremely important modes. The claimed detection
of g modes was obtained from the analysis of the power spectrum of
the time series of round-trip travel time of p modes. <BR /> Aims:
The goal of this paper is to reproduce these results on which the
claims are based for confirming or invalidating the detection of
g modes with the method used to make the claims. <BR /> Methods: We
computed the time series of round-trip travel time using the procedure
given in Fossat et al. (2017, A&A, 604, A40), and used different
variations of the times series for comparison. We used the recently
calibrated GOLF data (published in Paper I) with different sampling,
different photomultipliers, different length of data for reproducing the
analysis. We also correlated the power spectrum with an asymptotic model
of g-mode frequencies in a similar manner to Fossat and Schmider (2018,
A&A, 612, L1). We devised a scheme for optimising the correlation
both for pure noise and for the GOLF data. <BR /> Results: We confirm
the analysis performed in Fossat et al. (2017) but draw different
conclusions. Their claims of detection of g modes cannot be confirmed
when changing parameters such as sampling interval, length of time
series, or photomultipliers. Other instrument such as GONG and BiSON do
not confirm their detection. We also confirm the analysis performed in
Fossat and Schmider (2018), but again draw different conclusions. For
GOLF, the correlation of the power spectrum with the asymptotic model of
g-mode frequencies for l = 1 and l = 2 show a high correlation at lag=0
and at lag corresponding to the rotational splitting ν<SUB>l</SUB>,
but the same occurs for pure noise due to the large number of peaks
present in the model. In addition, other very different parameters
defining the asymptotic model also provide a high correlation at these
lags. We conclude that the detection performed in Fossat and Schmider
(2018) is an artefact of the methodology.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Asymmetry of oscillations in 43
Kepler stars (Benomar+, 2018)
Authors: Benomar, O.; Goupil, M.; Belkacem, K.; Appourchaux, T.;
Nielsen, M. B.; Bazot, M.; Gizon, L.; Hanasoge, S.; Sreenivasan,
K. R.; Marchand, B.
2019yCat..18570119B Altcode:
In this work, the considered ensemble of stars is a subset of the Kepler
LEGACY sample (Lund+ 2017, J/ApJ/835/172). We selected 43 stars for
analysis out of 66 of the LEGACY sample. The current analysis uses the
unweighted power spectra provided by the Kepler Asteroseismic Science
Operations Center (KASOC) pipeline (http://kasoc.phys.au.dk/). <P />(2
data files).
---------------------------------------------------------
Title: The Asteroseismic Target List for Solar-like Oscillators
Observed in 2 minute Cadence with the Transiting Exoplanet Survey
Satellite
Authors: Schofield, Mathew; Chaplin, William J.; Huber, Daniel;
Campante, Tiago L.; Davies, Guy R.; Miglio, Andrea; Ball, Warrick
H.; Appourchaux, Thierry; Basu, Sarbani; Bedding, Timothy R.;
Christensen-Dalsgaard, Jørgen; Creevey, Orlagh; García, Rafael A.;
Handberg, Rasmus; Kawaler, Steven D.; Kjeldsen, Hans; Latham, David W.;
Lund, Mikkel N.; Metcalfe, Travis S.; Ricker, George R.; Serenelli,
Aldo; Silva Aguirre, Victor; Stello, Dennis; Vanderspek, Roland
2019ApJS..241...12S Altcode: 2019arXiv190110148S
We present the target list of solar-type stars to be observed in
short-cadence (2 minute) for asteroseismology by the NASA Transiting
Exoplanet Survey Satellite (TESS) during its 2 year nominal survey
mission. The solar-like Asteroseismic Target List (ATL) is comprised
of bright, cool main-sequence and subgiant stars and forms part of the
larger target list of the TESS Asteroseismic Science Consortium. The
ATL uses the Gaia Data Release 2 and the Extended Hipparcos Compilation
(XHIP) to derive fundamental stellar properties, to calculate detection
probabilities, and to produce a rank-ordered target list. We provide a
detailed description of how the ATL was produced and calculate expected
yields for solar-like oscillators based on the nominal photometric
performance by TESS. We also provide a publicly available source code
that can be used to reproduce the ATL, thereby enabling comparisons
of asteroseismic results from TESS with predictions from synthetic
stellar populations.
---------------------------------------------------------
Title: First measurements of Jupiter's zonal winds with visible
imaging spectroscopy
Authors: Gonçalves, Ivan; Schmider, F. X.; Gaulme, Patrick;
Morales-Juberías, Raúl; Guillot, Tristan; Rivet, Jean-Pierre;
Appourchaux, Thierry; Boumier, Patrick; Jackiewicz, Jason; Sato,
Bun'ei; Ida, Shigeru; Ikoma, Masahiro; Mékarnia, Djamel; Underwood,
Thomas A.; Voelz, David
2019Icar..319..795G Altcode:
We present the first measurements of Jupiter's wind profile ever
obtained with Doppler velocity measurements in the visible. Hitherto,
knowledge about atmospheric dynamics has been obtained with
cloud-tracking techniques, which consist of tracking visible features
from images taken at different dates. However, cloud tracking indicates
the motion of large cloud structures, which is an indication of
the speed of iso-pressure regions, rather than the speed of the
actual atmospheric particles. Doppler imaging is as challenging -
motions are usually less than 100 m s-<SUP>1</SUP> - as appealing
because it measures the speed of cloud particles instead of large
cloud structures. Significant difference could appear in the case of
atmospheric waves interfering with cloud structures. Here we present
the first scientific results of a Doppler imaging spectrometer that
is dedicated to giant-planet seismology and atmospheric dynamics by
providing instantaneous line-of-sight-velocity maps of the planets of
the solar system. The instrument has been developed in the framework
of the projects JOVIAL (Jovian Oscillations through Velocity Images At
several Longitudes) and JIVE in NM (Jovian Interiors from Velocimetry
Experiment in New Mexico). It is a Fourier transform spectrometer with a
fixed optical path difference working in the mid-visible domain, which
monitors the position of solar Fraunhofer lines that are reflected
in the planets' upper atmospheres. After describing the instrument
principle and the different steps of data reduction, we report
measurement of the average zonal wind speed of Jupiter, as a function
of latitude, from datasets obtained in 2015 and 2016 with two different
telescopes, when the planet was close to its opposition. Our results
are consistent between the two years. We compare the results with wind
profiles obtained by cloud tracking on HST (Hubble Space Telescope)
images taken at the same epoch, and identify a significant discrepancy
in the North Equatorial Belt and northern part of the Equatorial Zone.
---------------------------------------------------------
Title: Searching for g modes. I. A new calibration of the GOLF
instrument
Authors: Appourchaux, T.; Boumier, P.; Leibacher, J. W.; Corbard, T.
2018A&A...617A.108A Altcode: 2018arXiv180700998A
Context. The recent claims of g-mode detection have restarted the
search for these potentially extremely important modes. These claims
can be reassessed in view of the different data sets available from
the SoHO instruments and ground-based instruments. <BR /> Aims: We
produce a new calibration of the GOLF data with a more consistent
p-mode amplitude and a more consistent time shift correction compared
to the time series used in the past. <BR /> Methods: The calibration
of 22 yr of GOLF data is done with a simpler approach that uses
only the predictive radial velocity of the SoHO spacecraft as a
reference. Using p modes, we measure and correct the time shift between
ground- and space-based instruments and the GOLF instrument. <BR />
Results: The p-mode velocity calibration is now consistent to within
a few percent with other instruments. The remaining time shifts are
within ±5 s for 99.8% of the time series. <P />The new calibrated
series (FITS) are available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/617/A108">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/617/A108</A>
---------------------------------------------------------
Title: First measurements of the Jovian zonal winds profile through
visible Doppler spectroscopy
Authors: Schmider, François-Xavier; Goncalves, Ivan; Gaulme, Patrick;
Morales-Jubieras, Raul; Guillot, Tristan; Appourchaux, Thierry;
Boumier, Patrick; Jackiewicz, Jason; Underwood, Thomas; Voelz, David;
Sato, Bun'ei; Ida, Shigeru; Ikoma, Masahiro; Rivet, Jean-Pierre
2018EPSC...12..433S Altcode:
We present the first measurements of Jupiter's wind profile ever
obtained with radial-velocity measurements. We report measurement of
the average zonal wind speed of Jupiter, as function of latitude, from
datasets obtained in 2016 and 2017 during the planet's opposition. We
compare our results with simultaneous wind profiles obtained by cloud
tracking from Hubble-space-telescope images, and point out a significant
discrepancy at the latitude of the hot spots in the northern equatorial
band, around 5° N.
---------------------------------------------------------
Title: Asteroseismic and orbital analysis of the triple star system
HD 188753 observed by Kepler
Authors: Marcadon, F.; Appourchaux, T.; Marques, J. P.
2018A&A...617A...2M Altcode: 2018arXiv180409296M
Context. The NASA Kepler space telescope has detected solar-like
oscillations in several hundreds of single stars, thereby providing a
way to determine precise stellar parameters using asteroseismology. <BR
/> Aims: In this work, we aim to derive the fundamental parameters of
a close triple star system, HD 188753, for which asteroseismic and
astrometric observations allow independent measurements of stellar
masses. <BR /> Methods: We used six months of Kepler photometry
available for HD 188753 to detect the oscillation envelopes of the
two brightest stars. For each star, we extracted the individual mode
frequencies by fitting the power spectrum using a maximum likelihood
estimation approach. We then derived initial guesses of the stellar
masses and ages based on two seismic parameters and on a characteristic
frequency ratio, and modelled the two components independently with
the stellar evolution code CESTAM. In addition, we derived the masses
of the three stars by applying a Bayesian analysis to the position
and radial-velocity measurements of the system. <BR /> Results:
Based on stellar modelling, the mean common age of the system is
10.8 ± 0.2 Gyr and the masses of the two seismic components are
M<SUB>A</SUB> = 0.99 ± 0.01 M<SUB>⊙</SUB> and M<SUB>Ba</SUB>
= 0.86 ± 0.01 M<SUB>⊙</SUB>. From the mass ratio of the close
pair, M<SUB>Bb</SUB>/M<SUB>Ba</SUB> = 0.767 ± 0.006, the mass of
the faintest star is M<SUB>Bb</SUB> = 0.66 ± 0.01 M<SUB>⊙</SUB>
and the total seismic mass of the system is then M<SUB>syst</SUB> =
2.51 ± 0.02 M<SUB>⊙</SUB>. This value agrees perfectly with the
total mass derived from our orbital analysis, M<SUB>syst</SUB> =
2.51<SUB>-0.18</SUB><SUP>+0.20</SUP> M<SUB>⊙</SUB>, and leads to
the best current estimate of the parallax for the system, π = 21.9
± 0.2 mas. In addition, the minimal relative inclination between the
inner and outer orbits is 10.9° ± 1.5°, implying that the system
does not have a coplanar configuration.
---------------------------------------------------------
Title: The High Resolution Telescope (HRT) of the Polarimetric and
Helioseismic Imager (PHI) onboard Solar Orbiter
Authors: Gandorfer, A.; Grauf, B.; Staub, J.; Bischoff, J.; Woch, J.;
Hirzberger, J.; Solanki, S. K.; Álvarez-Herrero, A.; García Parejo,
P.; Schmidt, W.; Volkmer, R.; Appourchaux, T.; del Toro Iniesta, J. C.
2018SPIE10698E..4NG Altcode:
Solar Orbiter is a joint mission of ESA and NASA scheduled for
launch in 2020. Solar Orbiter is a complete and unique heliophysics
mission, combining remote sensing and in-situ analysis; its special
elliptical orbit allows viewing the Sun from a distance of only 0.28
AU, and - leaving the ecliptic plane - to observe the solar poles from
a hitherto unexplored vantage point. One of the key instruments for
Solar Orbiter's science is the "Polarimetric and Helioseismic Imager"
(PHI), which will provide maps of the solar surface magnetic fields and
the gas flows on the visible solar surface. Two telescopes, a full disc
imager, and a high resolution channel feed a common Fabry-Perot based
tunable filter and thus allow sampling a single Fraunhofer line at 617.3
nm with high spectral resolution; a polarization modulation system
makes the system sensitive to the full state of polarization. From
the analysis of the Doppler shift and the magnetically induced Zeeman
polarization in this line, the magnetic field and the line-of-sight
gas motions can be detected for each point in the image. In this
paper we describe the opto-mechanical system design of the high
resolution telescope. It is based on a decentred Ritchey-Chrétien
two-mirror telescope. The telescope includes a Barlow type magnifier
lens group, which is used as in-orbit focus compensator, and a beam
splitter, which sends a small fraction of the collected light onto
a fast camera, which provides the error signals for the actively
controlled secondary mirror compensating for spacecraft jitter and other
disturbances. The elliptical orbit of the spacecraft poses high demands
on the thermo-mechanical stability. The varying size of the solar disk
image requires a special false-light suppression architecture, which is
briefly described. In combination with a heat-rejecting entrance window,
the optical energy impinging on the polarimetric and spectral analysis
system is efficiently reduced. We show how the design can preserve the
diffraction-limited imaging performance over the design temperature
range of -20°C to +60°C. The decentred hyperbolical mirrors require
special measures for the inter-alignment and their alignment with
respect to the mechanical structure. A system of alignment flats and
mechanical references is used for this purpose. We will describe the
steps of the alignment procedure, and the dedicated optical ground
support equipment, which are needed to reach the diffraction limited
performance of the telescope. We will also report on the verification
of the telescope performance, both - in ambient condition - and in
vacuum at different temperatures.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Sun velocities from GOLF instrument
(Appourchaux+, 2018)
Authors: Appourchaux, T.; Boumier, P.; Leibacher, J. W.; Corbard, T.
2018yCat..36170108A Altcode:
Three time series as FITS file comprising 34797600 data points of GOLF
velocity in m/s sampled at 20 sec (no time provided). The time series
starts on April 11, 1996 0:00 UT and ends on April 10, 2018 23:59:40
UT. The time series are provided for the photomultipliers PM1 and PM2,
and their arithmetic average. <P />(2 data files).
---------------------------------------------------------
Title: Exploring the poles of the Sun: POLAR Investigation of the Sun
(POLARIS+)
Authors: Appourchaux, Thierry
2018tess.conf11001A Altcode:
The POLAR Investigation of the Sun (POLARIS+) idea is one that has
been developed over a number of years, and is supported by scientists
in Europe, US, India and Japan so far. It uses a combination of a
gravity assist and solar sail propulsion to place a spacecraft in a
0.48 AU circular orbit around the Sun with an inclination of 75º
with respect to solar equator. In this orbit, at least 59% of the
time will be spent at latitudes higher than the maximum latitude
reached by Solar Orbiter (»32º). This first extended view of the
high-latitude regions of the Sun will enable crucial observations
not possible from the ecliptic viewpoint or from Solar Orbiter. While
Solar Orbiter will give the first glimpse of the high latitude magnetic
field and flows to probe the solar dynamo, it does not have sufficient
viewing of the polar regions to achieve POLARIS+ primary objective:
determining the relation between the magnetism and dynamics of the
Sun's polar regions and the solar cycle. <P />The scientific payload
needed to achieve these objectives consists of a set of remote-sensing
instruments. All instruments have a very high TRL being derived
from past and current missions such as Solar Orbiter. The payload
will consist of remote sensing instruments: <li>Dopplergraph
and magnetograph imager</li> <li>White-light coronagraph
(classical and heliospheric)</li> <li>EUV imager</li>
<li>UV spectrograph</li> <li>Total Solar Irradiance
monitor</li> <P />All imaging instruments will have a typical
resolution of 2 to 4 arcseconds. In-situ instruments could also be
considered as an interesting addition for following up on the success
of the ESA's Ulysses mission. <P />Extended observations from high
latitudes will revolutionize our understanding of the internal structure
and dynamics of the Sun and its atmosphere. The rapid, 4-month polar
orbit (allowed by the use of solar sails) combined with a suite of
remote-sensing instrumentation further enables unprecedented studies
of the physical connection between the Sun and the corona. Moreover,
POLARIS+ serves as a pathfinder for a permanent solar polar sentinel
for space-weather prediction in support of NASA's Vision for Space
Exploration, of ESA's Space Situational Awareness and a broad range
of other programs affected by space weather.
---------------------------------------------------------
Title: Asymmetry of Line Profiles of Stellar Oscillations Measured
by Kepler for Ensembles of Solar-like Oscillators: Impact on Mode
Frequencies and Dependence on Effective Temperature
Authors: Benomar, O.; Goupil, Mjo.; Belkacem, K.; Appourchaux, T.;
Nielsen, M. B.; Bazot, M.; Gizon, L.; Hanasoge, S.; Sreenivasan,
K. R.; Marchand, B.
2018ApJ...857..119B Altcode: 2018arXiv180406117B
Oscillation properties are usually measured by fitting symmetric
Lorentzian profiles to the power spectra of Sun-like stars. However,
the line profiles of solar oscillations have been observed to be
asymmetrical for the Sun. The physical origin of this line asymmetry is
not fully understood; though, it should depend on the depth dependence
of the source of wave excitation (convective turbulence) and details of
the observable (velocity or intensity). For oscillations of the Sun,
it has been shown that neglecting the asymmetry leads to systematic
errors in the frequency determination. This could subsequently
affect the results of seismic inferences of the solar internal
structure. Using light curves from the Kepler spacecraft, we have
measured mode asymmetries in 43 stars. We confirm that neglecting the
asymmetry leads to systematic errors that can exceed the 1σ confidence
intervals for seismic observations longer than one year. Therefore,
the application of an asymmetric Lorentzian profile should be favored
to improve the accuracy of the internal stellar structure and stellar
fundamental parameters. We also show that the asymmetry changes sign
between cool Sun-like stars and hotter stars. This provides the best
constraints to date on the location of the excitation sources across
the Hertzsprung-Russel diagram.
---------------------------------------------------------
Title: Helioseismology: Observations and Space Missions
Authors: Palle, P. L.; Appourchaux, T.; Christensen-Dalsgaard, J.;
Garcia, R. A.
2018arXiv180200674P Altcode:
The great success of Helioseismology resides in the remarkable
progress achieved in the understanding of the structure and dynamics
of the solar interior. This success mainly relies on the ability to
conceive, implement, and operate specific instrumentation with enough
sensitivity to detect and measure small fluctuations (in velocity
and/or intensity) on the solar surface that are well below one meter
per second or a few parts per million. Furthermore the limitation of
the ground observations imposing the day-night cycle (thus a periodic
discontinuity in the observations) was overcome with the deployment of
ground-based networks --properly placed at different longitudes all
over the Earth-- allowing longer and continuous observations of the
Sun and consequently increasing their duty cycles. In this chapter,
we start by a short historical overview of helioseismology. Then we
describe the different techniques used to do helioseismic analyses along
with a description of the main instrumental concepts. We in particular
focus on the instruments that have been operating long enough to study
the solar magnetic activity. Finally, we give a highlight of the main
results obtained with such high-duty cycle observations (>80%)
lasting over the last few decades.
---------------------------------------------------------
Title: VizieR Online Data Catalog: 61 main-sequence and subgiant
oscillations (Appourchaux+, 2012)
Authors: Appourchaux, T.; Chaplin, W. J.; Garcia, R. A.; Gruberbauer,
M.; Verner, G. A.; Antia, H. M.; Benomar, O.; Campante, T. L.; Davies,
G. R.; Deheuvels, S.; Handberg, R.; Hekker, S.; Howe, R.; Regulo,
C.; Salabert, D.; Bedding, T. R.; White, T. R.; Ballot, J.; Mathur,
S.; Silva Aguirre, V.; Elsworth, Y. P.; Basu, S.; Gilliland, R. L.;
Christensen-Dalsgaard, J.; Kjeldsen, H.; Uddin, K.; Stumpe, M. C.;
Barclay, T.
2017yCat..35430054A Altcode:
Kepler observations are obtained in two different operating
modes: long cadence (LC) and short cadence (SC) (Gilliland et al.,
2010ApJ...713L.160G; Jenkins et al., 2010ApJ...713L..87J). This work is
based on SC data. For the brightest stars (down to Kepler magnitude,
Kp~=12), SC observations can be obtained for a limited number of
stars (up to 512 at any given time) with a faster sampling cadence
of 58.84876s (Nyquist frequency of ~8.5mHz), which permits a more
precise transit timing and the performance of asteroseismology. Kepler
observations are divided into three-month-long quarters (Q). A subset
of 61 solar-type stars observed during quarters Q5-Q7 (March 22,
2010 to December 22, 2010) were chosen because they have oscillation
modes with high signal-to-noise ratios. This length of data gives a
frequency resolution of about 0.04uHz. <P />(2 data files).
---------------------------------------------------------
Title: Conception and test of Echoes, a spectro-imager dedicated to
the seismology of Jupiter
Authors: Soulat, L.; Schmider, F. -X.; Robbe-Dubois, S.; Appourchaux,
T.; Gaulme, P.; Bresson, Y.; Gay, J.; Daban, J. -B.; Gouvret, C.
2017SPIE10564E..1VS Altcode:
Echoes is a project of a spaceborne Doppler Spectro-Imager (DSI) which
has been proposed as payload to the JUICE mission project selected
in the Cosmic Vision program of the European Space Agency (ESA). It
is a Fourier transform spectrometer which measures phase shifts in
the interference patterns induced by Doppler shifts of spectral lines
reflected at the surface of the planet. Dedicated to the seismology of
Jupiter, the instrument is designed to analyze the periodic movements
induced by internal acoustic modes of the planet. It will allow
the knowledge of the internal structure of Jupiter, in particular
of the central region, which is essential for the comprehension of
the scenario of the giant planets' formation. The optical design is
based on a modified Mach-Zehnder interferometer operating in the
visible domain and takes carefully into account the sensitivity
of the optical path difference to the temperature. The instrument
produces simultaneously four images in quadrature which allows the
measurement of the phase without being contaminated by the continuum
component of the incident light. We expect a noise level less than 1
cm<SUP>2</SUP>s<SUP>-2</SUP>µHz<SUP>-1</SUP> in the frequency range
[0.5 -10] mHz. In this paper, we present the prototype implemented
at the Observatoire de la Côte d'Azur (OCA) in collaboration with
Institut d'Astrophysique Spatiale (IAS) to study the real performances
in laboratory and to demonstrate the capability to reach the required
Technology Readiness Level 5.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Asterosismology for solar analogues
16 Cyg A/B (Davies+, 2015)
Authors: Davies, G. R.; Chaplin, W. J.; Farr, W. M.; Garcia, R. A.;
Lund, M. N.; Mathis, S.; Metcalfe, T. S.; Appourchaux, T.; Basu, S.;
Benomar, O.; Campante, T. L.; Ceillier, T.; Elsworth, Y.; Handberg,
R.; Salabert, D.; Stello, D.
2017yCat..74462959D Altcode:
Both 16 Cyg A and B are brighter (V~6) than the saturation limit for
which Kepler observations were designed. However, it was possible to
capture the full stellar flux by using custom photometric aperture
masks. Thus, 928 d of short-cadence observations (Gilliland et
al. 2010ApJ...713L.160G) - from Quarter 7 to 16 - were generated using
simple aperture photometry (Jenkins et al. 2010ApJ...713L..87J) and
then corrected for instrumental perturbations following the methods
described by Garcia et al. (2011MNRAS.414L...6G). The final light
curves used for asteroseismic analyses were high-pass filtered using
a triangular smooth of 4 d width and have a duty cycle of 90.5 per
cent. The power density spectra were computed using a Lomb-Scargle
algorithm. <P />(2 data files).
---------------------------------------------------------
Title: Definition of a metrology servo-system for a solar imaging
fourier transform spectrometer working in the far UV (IFTSUV)
Authors: Ruiz de Galarreta Fanju, C.; Philippon, A.; Bouzit, M.;
Appourchaux, T.; Vial, J. -C.; Maillard, J. -P.; Lemaire, P.
2017SPIE10564E..3ER Altcode:
The understanding of the solar outer atmosphere requires a simultaneous
combination of imaging and spectral observations concerning the far UV
lines that arise from the high chromospheres up to the corona. These
observations must be performed with enough spectral, spatial and
temporal resolution to reveal the small atmospheric structures and to
resolve the solar dynamics. An Imaging Fourier Transform Spectrometer
working in the far-UV (IFTSUV, Figure 1) is an attractive instrumental
solution to fulfill these requirements. However, due to the short
wavelength, to preserve IFTSUV spectral precision and Signal to Noise
Ratio (SNR) requires a high optical surface quality and a very accurate
(linear and angular) metrology to maintain the optical path difference
(OPD) during the entire scanning process by: optical path difference
sampling trigger; and dynamic alignment for tip/tilt compensation
(Figure 2).
---------------------------------------------------------
Title: PLATO as it is : A legacy mission for Galactic archaeology
Authors: Miglio, A.; Chiappini, C.; Mosser, B.; Davies, G. R.;
Freeman, K.; Girardi, L.; Jofré, P.; Kawata, D.; Rendle, B. M.;
Valentini, M.; Casagrande, L.; Chaplin, W. J.; Gilmore, G.; Hawkins,
K.; Holl, B.; Appourchaux, T.; Belkacem, K.; Bossini, D.; Brogaard,
K.; Goupil, M. -J.; Montalbán, J.; Noels, A.; Anders, F.; Rodrigues,
T.; Piotto, G.; Pollacco, D.; Rauer, H.; Prieto, C. Allende; Avelino,
P. P.; Babusiaux, C.; Barban, C.; Barbuy, B.; Basu, S.; Baudin, F.;
Benomar, O.; Bienaymé, O.; Binney, J.; Bland-Hawthorn, J.; Bressan,
A.; Cacciari, C.; Campante, T. L.; Cassisi, S.; Christensen-Dalsgaard,
J.; Combes, F.; Creevey, O.; Cunha, M. S.; Jong, R. S.; Laverny, P.;
Degl'Innocenti, S.; Deheuvels, S.; Depagne, É.; Ridder, J.; Matteo,
P. Di; Mauro, M. P. Di; Dupret, M. -A.; Eggenberger, P.; Elsworth,
Y.; Famaey, B.; Feltzing, S.; García, R. A.; Gerhard, O.; Gibson,
B. K.; Gizon, L.; Haywood, M.; Handberg, R.; Heiter, U.; Hekker,
S.; Huber, D.; Ibata, R.; Katz, D.; Kawaler, S. D.; Kjeldsen, H.;
Kurtz, D. W.; Lagarde, N.; Lebreton, Y.; Lund, M. N.; Majewski, S. R.;
Marigo, P.; Martig, M.; Mathur, S.; Minchev, I.; Morel, T.; Ortolani,
S.; Pinsonneault, M. H.; Plez, B.; Moroni, P. G. Prada; Pricopi, D.;
Recio-Blanco, A.; Reylé, C.; Robin, A.; Roxburgh, I. W.; Salaris,
M.; Santiago, B. X.; Schiavon, R.; Serenelli, A.; Sharma, S.; Aguirre,
V. Silva; Soubiran, C.; Steinmetz, M.; Stello, D.; Strassmeier, K. G.;
Ventura, P.; Ventura, R.; Walton, N. A.; Worley, C. C.
2017AN....338..644M Altcode: 2017arXiv170603778M
Deciphering the assembly history of the Milky Way is a formidable
task, which becomes possible only if one can produce high-resolution
chrono-chemo-kinematical maps of the Galaxy. Data from large-scale
astrometric and spectroscopic surveys will soon provide us with a
well-defined view of the current chemo-kinematical structure of the
Milky Way, but will only enable a blurred view on the temporal sequence
that led to the present-day Galaxy. As demonstrated by the (ongoing)
exploitation of data from the pioneering photometric missions CoRoT,
Kepler, and K2, asteroseismology provides the way forward: solar-like
oscillating giants are excellent evolutionary clocks thanks to the
availability of seismic constraints on their mass and to the tight
age-initial-mass relation they adhere to. In this paper we identify
five key outstanding questions relating to the formation and evolution
of the Milky Way that will need precise and accurate ages for large
samples of stars to be addressed, and we identify the requirements
in terms of number of targets and the precision on the stellar
properties that are needed to tackle such questions. By quantifying
the asteroseismic yields expected from PLATO for red-giant stars, we
demonstrate that these requirements are within the capabilities of the
current instrument design, provided that observations are sufficiently
long to identify the evolutionary state and allow robust and precise
determination of acoustic-mode frequencies. This will allow us to
harvest data of sufficient quality to reach a 10% precision in age. This
is a fundamental pre-requisite to then reach the more ambitious goal
of a similar level of accuracy, which will only be possible if we
have to hand a careful appraisal of systematic uncertainties on age
deriving from our limited understanding of stellar physics, a goal
which conveniently falls within the main aims of PLATO's core science.
---------------------------------------------------------
Title: SOLARIS: Solar Sail Investigation of the Sun
Authors: Appourchaux, Thierry; Auchère, Frédéric; Antonucci, Ester;
Gizon, Laurent; MacDonald, Malcolm; Hara, Hirohisa; Sekii, Takashi;
Moses, Daniel; Vourlidas, Angelos
2017arXiv170708193A Altcode:
In this paper, we detail the scientific objectives and outline
a strawman payload of the SOLAR sail Investigation of the Sun
(SOLARIS). The science objectives are to study the 3D structure
of the solar magnetic and velocity field, the variation of total
solar irradiance with latitude, and the structure of the corona. We
show how we can meet these science objective using solar-sail
technologies currently under development. We provide a tentative
mission profile considering several trade-off approaches. We also
provide a tentative mass budget breakdown and a perspective for a
programmatic implementation.
---------------------------------------------------------
Title: Kepler observations of the asteroseismic binary HD 176465
Authors: White, T. R.; Benomar, O.; Silva Aguirre, V.; Ball, W. H.;
Bedding, T. R.; Chaplin, W. J.; Christensen-Dalsgaard, J.; Garcia,
R. A.; Gizon, L.; Stello, D.; Aigrain, S.; Antia, H. M.; Appourchaux,
T.; Bazot, M.; Campante, T. L.; Creevey, O. L.; Davies, G. R.;
Elsworth, Y. P.; Gaulme, P.; Handberg, R.; Hekker, S.; Houdek,
G.; Howe, R.; Huber, D.; Karoff, C.; Marques, J. P.; Mathur, S.;
McQuillan, A.; Metcalfe, T. S.; Mosser, B.; Nielsen, M. B.; Régulo,
C.; Salabert, D.; Stahn, T.
2017A&A...601A..82W Altcode: 2016arXiv160909581W; 2016A&A...601A..82W
Binary star systems are important for understanding stellar structure
and evolution, and are especially useful when oscillations can be
detected and analysed with asteroseismology. However, only four
systems are known in which solar-like oscillations are detected in
both components. Here, we analyse the fifth such system, HD 176465,
which was observed by Kepler. We carefully analysed the system's
power spectrum to measure individual mode frequencies, adapting our
methods where necessary to accommodate the fact that both stars
oscillate in a similar frequency range. We also modelled the two
stars independently by fitting stellar models to the frequencies and
complementaryparameters. We are able to cleanly separate the oscillation
modes in both systems. The stellar models produce compatible ages and
initial compositions for the stars, as is expected from their common
and contemporaneous origin. Combining the individual ages, the system
is about 3.0 ± 0.5 Gyr old. The two components of HD 176465 are young
physically-similar oscillating solar analogues, the first such system
to be found, and provide important constraints for stellar evolution
and asteroseismology.
---------------------------------------------------------
Title: Future Mission Concepts for Helioseismology
Authors: Sekii, Takashi; Appourchaux, Thierry; Fleck, Bernhard;
Turck-Chièze, Sylvaine
2017hdsi.book..291S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Helioseismology with Solar Orbiter
Authors: Löptien, Björn; Birch, Aaron C.; Gizon, Laurent; Schou,
Jesper; Appourchaux, Thierry; Blanco Rodríguez, Julián; Cally,
Paul S.; Dominguez-Tagle, Carlos; Gandorfer, Achim; Hill, Frank;
Hirzberger, Johann; Scherrer, Philip H.; Solanki, Sami K.
2017hdsi.book..257L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Distant Mirror: Solar Oscillations Observed on Neptune by
the Kepler K2 Mission
Authors: Gaulme, P.; Rowe, J. F.; Bedding, T. R.; Benomar, O.;
Corsaro, E.; Davies, G. R.; Hale, S. J.; Howe, R.; Garcia, R. A.;
Huber, D.; Jiménez, A.; Mathur, S.; Mosser, B.; Appourchaux, T.;
Boumier, P.; Jackiewicz, J.; Leibacher, J.; Schmider, F. -X.; Hammel,
H. B.; Lissauer, J. J.; Marley, M. S.; Simon, A. A.; Chaplin, W. J.;
Elsworth, Y.; Guzik, J. A.; Murphy, N.; Silva Aguirre, V.
2016ApJ...833L..13G Altcode: 2016arXiv161204287G
Starting in 2014 December, Kepler K 2 observed Neptune continuously
for 49 days at a 1 minute cadence. The goals consisted of studying its
atmospheric dynamics, detecting its global acoustic oscillations, and
those of the Sun, which we report on here. We present the first indirect
detection of solar oscillations in intensity measurements. Beyond
the remarkable technical performance, it indicates how Kepler would
see a star like the Sun. The result from the global asteroseismic
approach, which consists of measuring the oscillation frequency
at maximum amplitude ν <SUB>max</SUB> and the mean frequency
separation between mode overtones Δν, is surprising as the ν
<SUB>max</SUB> measured from Neptune photometry is larger than the
accepted value. Compared to the usual reference ν <SUB>max,⊙</SUB>
= 3100 μHz, the asteroseismic scaling relations therefore make the
solar mass and radius appear larger by 13.8 ± 5.8% and 4.3 ± 1.9%,
respectively. The higher ν <SUB>max</SUB> is caused by a combination
of the value of ν <SUB>max,⊙</SUB>, being larger at the time
of observations than the usual reference from SOHO/VIRGO/SPM data
(3160 ± 10 μHz), and the noise level of the K 2 time series, being
10 times larger than VIRGO’s. The peak-bagging method provides
more consistent results: despite a low signal-to-noise ratio (S/N),
we model 10 overtones for degrees ℓ = 0, 1, 2. We compare the K 2
data with simultaneous SOHO/VIRGO/SPM photometry and BiSON velocity
measurements. The individual frequencies, widths, and amplitudes mostly
match those from VIRGO and BiSON within 1σ, except for the few peaks
with the lowest S/N.
---------------------------------------------------------
Title: Far side Helioseismology with Solar Orbiter
Authors: Appourchaux, T.; Birch, A.; Gizon, L. C.; Löptien, B.;
Schou, J.; Solanki, S. K.; del Toro Iniesta, J. C.; Gandorfer, A.;
Hirzberger, J.; Alvarez-Herrero, A.; Woch, J. G.; Schmidt, W.
2016AGUFMSH43A2554A Altcode:
The Solar Orbiter mission, to be launched in October 2018, will
carry a suite of remote sensing and in-situ instruments, including
the Polarimetric and Helioseismic Imager (PHI). PHI will deliver
high-cadence images of the Sun in intensity and Doppler velocity
suitable for carrying out novel helioseismic studies. The orbit
of the Solar Orbiter spacecraft will reach a solar latitude up to
34 degrees by the end of the extended mission and thus will enable
the first local helioseismology studies of the polar regions. The
full range of Earth-Sun-spacecraft angles provided by the orbit will
enable helioseismology from two vantage points by combining PHI with
another instrument: stereoscopic helioseismology will allow the study
of the deep solar interior and a better understanding of the physics
of solar oscillations in both quiet Sun and sunspots. In this paper
we will review the helioseismic objectives achievable with PHI, and
will also give a short status report of the development of the Flight
Model of PHI.
---------------------------------------------------------
Title: Detection of Solar-like Oscillations, Observational
Constraints, and Stellar Models for θ Cyg, the Brightest Star
Observed By the Kepler Mission
Authors: Guzik, J. A.; Houdek, G.; Chaplin, W. J.; Smalley, B.; Kurtz,
D. W.; Gilliland, R. L.; Mullally, F.; Rowe, J. F.; Bryson, S. T.;
Still, M. D.; Antoci, V.; Appourchaux, T.; Basu, S.; Bedding, T. R.;
Benomar, O.; Garcia, R. A.; Huber, D.; Kjeldsen, H.; Latham, D. W.;
Metcalfe, T. S.; Pápics, P. I.; White, T. R.; Aerts, C.; Ballot, J.;
Boyajian, T. S.; Briquet, M.; Bruntt, H.; Buchhave, L. A.; Campante,
T. L.; Catanzaro, G.; Christensen-Dalsgaard, J.; Davies, G. R.;
Doğan, G.; Dragomir, D.; Doyle, A. P.; Elsworth, Y.; Frasca, A.;
Gaulme, P.; Gruberbauer, M.; Handberg, R.; Hekker, S.; Karoff, C.;
Lehmann, H.; Mathias, P.; Mathur, S.; Miglio, A.; Molenda-Żakowicz,
J.; Mosser, B.; Murphy, S. J.; Régulo, C.; Ripepi, V.; Salabert,
D.; Sousa, S. G.; Stello, D.; Uytterhoeven, K.
2016ApJ...831...17G Altcode: 2016arXiv160701035G
θ Cygni is an F3 spectral type magnitude V = 4.48 main-sequence star
that was the brightest star observed by the original Kepler spacecraft
mission. Short-cadence (58.8 s) photometric data using a custom
aperture were first obtained during Quarter 6 (2010 June-September) and
subsequently in Quarters 8 and 12-17. We present analyses of solar-like
oscillations based on Q6 and Q8 data, identifying angular degree l = 0,
1, and 2 modes with frequencies of 1000-2700 μHz, a large frequency
separation of 83.9 ± 0.4 μHz, and maximum oscillation amplitude
at frequency ν <SUB>max</SUB> = 1829 ± 54 μHz. We also present
analyses of new ground-based spectroscopic observations, which,
combined with interferometric angular diameter measurements, give T
<SUB>eff</SUB> = 6697 ± 78 K, radius 1.49 ± 0.03 R <SUB>⊙</SUB>,
[Fe/H] = -0.02 ± 0.06 dex, and log g = 4.23 ± 0.03. We calculate
stellar models matching these constraints using the Yale Rotating
Evolution Code and the Asteroseismic Modeling Portal. The best-fit
models have masses of 1.35-1.39 M <SUB>⊙</SUB> and ages of 1.0-1.6
Gyr. θ Cyg’s T <SUB>eff</SUB> and log g place it cooler than the red
edge of the γ Doradus instability region established from pre-Kepler
ground-based observations, but just at the red edge derived from
pulsation modeling. The pulsation models show γ Dor gravity modes
driven by the convective blocking mechanism, with frequencies of 1-3
cycles per day (11 to 33 μHz). However, gravity modes were not seen
in Kepler data; one signal at 1.776 cycles per day (20.56 μHz) may
be attributable to a faint, possibly background, binary.
---------------------------------------------------------
Title: Oscillation mode linewidths and heights of 23 main-sequence
stars observed by Kepler (Corrigendum)
Authors: Appourchaux, T.; Antia, H. M.; Benomar, O.; Campante, T. L.;
Davies, G. R.; Handberg, R.; Howe, R.; Régulo, C.; Belkacem, K.;
Houdek, G.; García, R. A.; Chaplin, W. J.
2016A&A...595C...2A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Asteroseismic Potential of TESS: Exoplanet-host Stars
Authors: Campante, T. L.; Schofield, M.; Kuszlewicz, J. S.; Bouma,
L.; Chaplin, W. J.; Huber, D.; Christensen-Dalsgaard, J.; Kjeldsen,
H.; Bossini, D.; North, T. S. H.; Appourchaux, T.; Latham, D. W.;
Pepper, J.; Ricker, G. R.; Stassun, K. G.; Vanderspek, R.; Winn, J. N.
2016ApJ...830..138C Altcode: 2016arXiv160801138C
New insights on stellar evolution and stellar interior physics are
being made possible by asteroseismology. Throughout the course of the
Kepler mission, asteroseismology has also played an important role
in the characterization of exoplanet-host stars and their planetary
systems. The upcoming NASA Transiting Exoplanet Survey Satellite
(TESS) will be performing a near all-sky survey for planets that
transit bright nearby stars. In addition, its excellent photometric
precision, combined with its fine time sampling and long intervals of
uninterrupted observations, will enable asteroseismology of solar-type
and red-giant stars. Here we develop a simple test to estimate the
detectability of solar-like oscillations in TESS photometry of any given
star. Based on an all-sky stellar and planetary synthetic population,
we go on to predict the asteroseismic yield of the TESS mission,
placing emphasis on the yield of exoplanet-host stars for which we
expect to detect solar-like oscillations. This is done for both the
target stars (observed at a 2-minute cadence) and the full-frame-image
stars (observed at a 30-minute cadence). A similar exercise is also
conducted based on a compilation of known host stars. We predict that
TESS will detect solar-like oscillations in a few dozen target hosts
(mainly subgiant stars but also in a smaller number of F dwarfs), in up
to 200 low-luminosity red-giant hosts, and in over 100 solar-type and
red-giant known hosts, thereby leading to a threefold improvement in the
asteroseismic yield of exoplanet-host stars when compared to Kepler's.
---------------------------------------------------------
Title: Advances in the development of a Mach-Zehnder interferometric
Doppler imager for seismology of giant planets
Authors: Gonçalves, Ivan; Schmider, François-Xavier; Bresson, Yves;
Dejonghe, Julien; Preis, Olivier; Robbe-Dubois, Sylvie; Appourchaux,
Thierry; Boumier, Patrick; Leclec'h, Jean-Christophe; Morinaud,
Gilles; Gaulme, Patrick; Jackiewicz, Jason
2016SPIE.9908E..3MG Altcode:
The measurements of radial velocity fields on planets with a Doppler
Spectro-Imager allow the study of atmospheric dynamics of giant planets
and the detection of their acoustic oscillations. The frequencies of
these oscillations lead to the determination of the internal structure
by asteroseismology. A new imaging tachometer, based on a Mach-Zehnder
interferometer, has been developed to monitor the Doppler shift of solar
lines reflected at the surface of the planets. We present the principle
of this instrument. A prototype was designed and built, following
the specifications of a future space mission. The performance of the
prototype, both at the laboratory and on the sky, is presented here.
---------------------------------------------------------
Title: Measuring the extent of convective cores in low-mass stars
using Kepler data: toward a calibration of core overshooting
Authors: Deheuvels, S.; Brandão, I.; Silva Aguirre, V.; Ballot, J.;
Michel, E.; Cunha, M. S.; Lebreton, Y.; Appourchaux, T.
2016A&A...589A..93D Altcode: 2016arXiv160302332D
Context. Our poor understanding of the boundaries of convective
cores generates large uncertainties on the extent of these cores and
thus on stellar ages. The detection and precise characterization of
solar-like oscillations in hundreds of main-sequence stars by CoRoT
and Kepler has given the opportunity to revisit this problem. <BR />
Aims: Our aim is to use asteroseismology to consistently measure the
extent of convective cores in a sample of main-sequence stars whose
masses lie around the mass limit for having a convective core. <BR />
Methods: We first tested and validated a seismic diagnostic that was
proposed to probe the extent of convective cores in a model-dependent
way using the so-called r<SUB>010</SUB> ratios, which are built
with l = 0 and l = 1 modes. We applied this procedure to 24 low-mass
stars chosen among Kepler targets to optimize the efficiency of this
diagnostic. For this purpose, we computed grids of stellar models
with both the Cesam2k and mesa evolution codes, where the extensions
of convective cores were modeled either by an instantaneous mixing or
as a diffusion process. <BR /> Results: We found that 10 stars in our
sample are in fact subgiants. Among the other targets, were able to
unambiguously detect convective cores in eight stars, and we obtained
seismic measurements of the extent of the mixed core in these targets
with a good agreement between the Cesam2k and mesa codes. By performing
optimizations using the Levenberg-Marquardt algorithm, we then obtained
estimates of the amount of extra mixing beyond the core that is required
in Cesam2k to reproduce seismic observations for these eight stars,
and we showed that this can be used to propose a calibration of this
quantity. This calibration depends on the prescription chosen for the
extra mixing, but we found that it should also be valid for the code
mesa, provided the same prescription is used. <BR /> Conclusions:
This study constitutes a first step toward calibrating the extension
of convective cores in low-mass stars, which will help reduce the
uncertainties on the ages of these stars.
---------------------------------------------------------
Title: Helioseismology with Solar Orbiter
Authors: Löptien, Björn; Birch, Aaron C.; Gizon, Laurent; Schou,
Jesper; Appourchaux, Thierry; Blanco Rodríguez, Julián; Cally,
Paul S.; Dominguez-Tagle, Carlos; Gandorfer, Achim; Hill, Frank;
Hirzberger, Johann; Scherrer, Philip H.; Solanki, Sami K.
2015SSRv..196..251L Altcode: 2014arXiv1406.5435L; 2014SSRv..tmp...31L
The Solar Orbiter mission, to be launched in July 2017, will
carry a suite of remote sensing and in-situ instruments, including
the Polarimetric and Helioseismic Imager (PHI). PHI will deliver
high-cadence images of the Sun in intensity and Doppler velocity
suitable for carrying out novel helioseismic studies. The orbit of
the Solar Orbiter spacecraft will reach a solar latitude of up to
21<SUP>∘</SUP> (up to 34<SUP>∘</SUP> by the end of the extended
mission) and thus will enable the first local helioseismology studies of
the polar regions. Here we consider an array of science objectives to be
addressed by helioseismology within the baseline telemetry allocation
(51 Gbit per orbit, current baseline) and within the science observing
windows (baseline 3×10 days per orbit). A particularly important
objective is the measurement of large-scale flows at high latitudes
(rotation and meridional flow), which are largely unknown but play an
important role in flux transport dynamos. For both helioseismology
and feature tracking methods convection is a source of noise in
the measurement of longitudinally averaged large-scale flows, which
decreases as T <SUP>-1/2</SUP> where T is the total duration of the
observations. Therefore, the detection of small amplitude signals (e.g.,
meridional circulation, flows in the deep solar interior) requires long
observation times. As an example, one hundred days of observations at
lower spatial resolution would provide a noise level of about three m/s
on the meridional flow at 80<SUP>∘</SUP> latitude. Longer time-series
are also needed to study temporal variations with the solar cycle. The
full range of Earth-Sun-spacecraft angles provided by the orbit will
enable helioseismology from two vantage points by combining PHI with
another instrument: stereoscopic helioseismology will allow the study
of the deep solar interior and a better understanding of the physics
of solar oscillations in both quiet Sun and sunspots. We have used a
model of the PHI instrument to study its performance for helioseismology
applications. As input we used a 6 hr time-series of realistic solar
magneto-convection simulation (Stagger code) and the SPINOR radiative
transfer code to synthesize the observables. The simulated power
spectra of solar oscillations show that the instrument is suitable for
helioseismology. In particular, the specified point spread function,
image jitter, and photon noise are no obstacle to a successful mission.
---------------------------------------------------------
Title: Future Mission Concepts for Helioseismology
Authors: Sekii, Takashi; Appourchaux, Thierry; Fleck, Bernhard;
Turck-Chièze, Sylvaine
2015SSRv..196..285S Altcode: 2015SSRv..tmp...15S
Future space-mission concepts currently discussed in the helioseismology
community are reviewed. One popular idea is to observe the Sun from high
latitudes, to explore the polar regions as well as to probe the deep
interior using stereoscopic techniques, by combining observations from
high latitudes with observations from within the ecliptic plane. Another
idea is to stay within the ecliptic plane but still aim for stereoscopic
helioseismology for deep layers. A new instrument and a novel mission
concept for studying the solar core regions are also discussed.
---------------------------------------------------------
Title: A seismic and gravitationally bound double star observed by
Kepler. Implication for the presence of a convective core
Authors: Appourchaux, T.; Antia, H. M.; Ball, W.; Creevey, O.;
Lebreton, Y.; Verma, K.; Vorontsov, S.; Campante, T. L.; Davies,
G. R.; Gaulme, P.; Régulo, C.; Horch, E.; Howell, S.; Everett, M.;
Ciardi, D.; Fossati, L.; Miglio, A.; Montalbán, J.; Chaplin, W. J.;
García, R. A.; Gizon, L.
2015A&A...582A..25A Altcode:
Context. Solar-like oscillations have been observed by Kepler and CoRoT
in many solar-type stars, thereby providing a way to probe stars using
asteroseismology. <BR /> Aims: The derivation of stellar parameters
has usually been done with single stars. The aim of the paper is to
derive the stellar parameters of a double-star system (HIP 93511),
for which an interferometric orbit has been observed along with
asteroseismic measurements. <BR /> Methods: We used a time series
of nearly two years of data for the double star to detect the two
oscillation-mode envelopes that appear in the power spectrum. Using
a new scaling relation based on luminosity, we derived the radius and
mass of each star. We derived the age of each star using two proxies:
one based upon the large frequency separation and a new one based
upon the small frequency separation. Using stellar modelling, the mode
frequencies allowed us to derive the radius, the mass, and the age of
each component. In addition, speckle interferometry performed since 2006
has enabled us to recover the orbit of the system and the total mass
of the system. <BR /> Results: From the determination of the orbit,
the total mass of the system is 2.34<SUB>-0.33</SUB><SUP>+0.45</SUP>
M<SUB>⊙</SUB>. The total seismic mass using scaling relations
is 2.47 ± 0.07 M<SUB>⊙</SUB>. The seismic age derived using the
new proxy based upon the small frequency separation is 3.5 ± 0.3
Gyr. Based on stellar modelling, the mean common age of the system is
2.7-3.9 Gyr. The mean total seismic mass of the system is 2.34-2.53
M<SUB>⊙</SUB> consistent with what we determined independently
with the orbit. The stellar models provide the mean radius, mass,
and age of the stars as R<SUB>A</SUB> = 1.82-1.87R<SUB>⊙</SUB>,
M<SUB>A</SUB> = 1.25-1.39 M<SUB>⊙</SUB>, Age<SUB>A</SUB> = 2.6-3.5
Gyr; R<SUB>B</SUB> = 1.22-1.25 R<SUB>⊙</SUB>, M<SUB>B</SUB> =
1.08-1.14 M<SUB>⊙</SUB>, Age<SUB>B</SUB> = 3.35-4.21 Gyr. The
models provide two sets of values for Star A: [1.25-1.27]
M<SUB>⊙</SUB> and [1.34-1.39] M<SUB>⊙</SUB>. We detect a
convective core in Star A, while Star B does not have any. For the
metallicity of the binary system of Z ≈ 0.02, we set the limit
between stars having a convective core in the range [1.14-1.25]
M<SUB>⊙</SUB>. <P />Appendices are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201526610/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: The Polarimetric and Helioseismic Imager for Solar Orbiter:
SO/PHI
Authors: Solanki, Sami K.; del Toro Iniesta, Jose Carlos; Woch,
Joachim; Gandorfer, Achim; Hirzberger, Johann; Schmidt, Wolfgang;
Appourchaux, Thierry; Alvarez-Herrero, Alberto
2015IAUS..305..108S Altcode: 2015arXiv150203368S
The Solar Orbiter is the next solar physics mission of the European
Space Agency, ESA, in collaboration with NASA, with a launch planned in
2018. The spacecraft is designed to approach the Sun to within 0.28 AU
at perihelion of a highly eccentric orbit. The proximity with the Sun
will also allow its observation at uniformly high resolution at EUV and
visible wavelengths. Such observations are central for learning more
about the magnetic coupling of the solar atmosphere. At a later phase
in the mission the spacecraft will leave the ecliptic and study the
enigmatic poles of the Sun from a heliographic latitude of up to 33°.
---------------------------------------------------------
Title: Asteroseismology of Solar-Type Stars with K2: Detection of
Oscillations in C1 Data
Authors: Chaplin, W. J.; Lund, M. N.; Handberg, R.; Basu, S.;
Buchhave, L. A.; Campante, T. L.; Davies, G. R.; Huber, D.; Latham,
D. W.; Latham, C. A.; Serenelli, A.; Antia, H. M.; Appourchaux, T.;
Ball, W. H.; Benomar, O.; Casagrande, L.; Christensen-Dalsgaard, J.;
Coelho, H. R.; Creevey, O. L.; Elsworth, Y.; García, R. A.; Gaulme,
P.; Hekker, S.; Kallinger, T.; Karoff, C.; Kawaler, S. D.; Kjeldsen,
H.; Lundkvist, M. S.; Marcadon, F.; Mathur, S.; Miglio, A.; Mosser,
B.; Régulo, C.; Roxburgh, I. W.; Silva Aguirre, V.; Stello, D.;
Verma, K.; White, T. R.; Bedding, T. R.; Barclay, T.; Buzasi, D. L.;
Dehuevels, S.; Gizon, L.; Houdek, G.; Howell, S. B.; Salabert, D.;
Soderblom, D. R.
2015PASP..127.1038C Altcode: 2015arXiv150701827C
We present the first detections by the NASA K2 Mission of oscillations
in solar-type stars, using short-cadence data collected during
K2 Campaign\,1 (C1). We understand the asteroseismic detection
thresholds for C1-like levels of photometric performance, and we
can detect oscillations in subgiants having dominant oscillation
frequencies around $1000\,\rm \mu Hz$. Changes to the operation of the
fine-guidance sensors are expected to give significant improvements
in the high-frequency performance from C3 onwards. A reduction in the
excess high-frequency noise by a factor of two-and-a-half in amplitude
would bring main-sequence stars with dominant oscillation frequencies as
high as ${\simeq 2500}\,\rm \mu Hz$ into play as potential asteroseismic
targets for K2.
---------------------------------------------------------
Title: Asteroseismic estimate of helium abundance of 16 Cyg A, B
Authors: Verma, Kuldeep; Faria, João P.; Antia, H. M.; Basu, Sarbani;
Mazumdar, Anwesh; Monteiro, Mário J. P. F. G.; Appourchaux, Thierry;
Chaplin, William J.; García, Rafael A.; Metcalfe, Travis S.
2015EPJWC.10106066V Altcode:
The helium ionization zone in a star leaves a characteristic signature
on its oscillation frequencies, which can be used to estimate the
helium content in the envelope of the star. We use the oscillation
frequencies of 16 Cyg A and B, obtained using 2.5 years of Kepler data,
to estimate the envelope helium abundance of these stars. We find the
envelope helium abundance to lie in the range 0.231-0.251 for 16 Cyg
A and 0.218-0.266 for 16 Cyg B.
---------------------------------------------------------
Title: An attempt to calibrate core overshooting using the seismic
properties of low-mass stars
Authors: Deheuvels, S.; Silva Aguirre, V.; Cunha, M. S.; Appourchaux,
T.; Ballot, J.; Brandão, I.; Lebreton, Y.; Michel, E.
2015EPJWC.10101013D Altcode:
The sizes of stellar convective cores remain uncertain because of our
poor understanding of the interface between convective and radiative
zones. The very high precision of the seismic data provided by the CoRoT
and Kepler space missions offers a great opportunity to search for the
signature of convective cores in main-sequence stars. We here validate
the seismic diagnostic based on the r<SUB>010</SUB> ratios, which has
been proposed to probe the size of convective cores, and we use it on
a sample of 24 specially chosen Kepler targets. We thus constrain the
extension of the core in 14 targets and find a tendency of the core
extension to increase with stellar mass in this mass range. These
results will be presented in more detail in a paper in preparation.
---------------------------------------------------------
Title: Helioseismology: Observations and space missions
Authors: Pallé, P. L.; Appourchaux, T.; Christensen-Dalsgaard, J.;
Garcxía, I. A.
2015exse.book...25P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Asteroseismology observations and space missions
Authors: Appourchaux, T.; Grundahl, F.
2015exse.book...11A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Asteroseismic inference on rotation, gyrochronology and
planetary system dynamics of 16 Cygni
Authors: Davies, G. R.; Chaplin, W. J.; Farr, W. M.; García, R. A.;
Lund, M. N.; Mathis, S.; Metcalfe, T. S.; Appourchaux, T.; Basu, S.;
Benomar, O.; Campante, T. L.; Ceillier, T.; Elsworth, Y.; Handberg,
R.; Salabert, D.; Stello, D.
2015MNRAS.446.2959D Altcode: 2014arXiv1411.1359D
The solar analogues 16 Cyg A and B are excellent asteroseismic targets
in the Kepler field of view and together with a red dwarf and a Jovian
planet form an interesting system. For these more evolved Sun-like
stars we cannot detect surface rotation with the current Kepler
data but instead use the technique of asteroseimology to determine
rotational properties of both 16 Cyg A and B. We find the rotation
periods to be 23.8^{+1.5}_{-1.8} and 23.2^{+11.5}_{-3.2} d, and
the angles of inclination to be 56^{+6}_{-5}° and 36^{+17}_{-7}°,
for A and B, respectively. Together with these results we use the
published mass and age to suggest that, under the assumption of a
solar-like rotation profile, 16 Cyg A could be used when calibrating
gyrochronology relations. In addition, we discuss the known 16 Cyg B
star-planet eccentricity and measured low obliquity which is consistent
with Kozai cycling and tidal theory.
---------------------------------------------------------
Title: Building galaxies, stars, planets and the ingredients for life
between the stars. The science behind the European Ultraviolet-Visible
Observatory
Authors: Gómez de Castro, Ana I.; Appourchaux, Thierry; Barstow,
Martin A.; Barthelemy, Mathieu; Baudin, Frederic; Benetti, Stefano;
Blay, Pere; Brosch, Noah; Bunce, Emma; de Martino, Domitilla;
Deharveng, Jean-Michel; Ferlet, Roger; France, Kevin; García, Miriam;
Gänsicke, Boris; Gry, Cecile; Hillenbrand, Lynne; Josselin, Eric;
Kehrig, Carolina; Lamy, Laurent; Lapington, Jon; Lecavelier des
Etangs, Alain; LePetit, Frank; López-Santiago, Javier; Milliard,
Bruno; Monier, Richard; Naletto, Giampiero; Nazé, Yael; Neiner,
Coralie; Nichols, Jonathan; Orio, Marina; Pagano, Isabella; Peroux,
Céline; Rauw, Gregor; Shore, Steven; Spaans, Marco; Tovmassian,
Gagik; ud-Doula, Asif; Vilchez, José
2014Ap&SS.354..229G Altcode: 2014Ap&SS.tmp..185G; 2013arXiv1306.3358G
This contribution gathers the contents of the white paper submitted
by the UV community to the Call issued by the European Space Agency
in March 2013, for the definition of the L2 and L3 missions in the ESA
science program. We outlined the key science that a large UV facility
would make possible and the instrumentation to be implemented. The
growth of luminous structures and the building blocks of life in the
Universe began as primordial gas was processed in stars and mixed at
galactic scales. The mechanisms responsible for this development are
not well-understood and have changed over the intervening 13 billion
years. To follow the evolution of matter over cosmic time, it is
necessary to study the strongest (resonance) transitions of the most
abundant species in the Universe. Most of them are in the ultraviolet
(UV; 950 Å-3000 Å) spectral range that is unobservable from the
ground. A versatile space observatory with UV sensitivity a factor
of 50-100 greater than existing facilities will revolutionize our
understanding of the Universe. Habitable planets grow in protostellar
discs under ultraviolet irradiation, a by-product of the star-disk
interaction that drives the physical and chemical evolution of discs
and young planetary systems. The electronic transitions of the most
abundant molecules are pumped by this UV field, providing unique
diagnostics of the planet-forming environment that cannot be accessed
from the ground. Earth's atmosphere is in constant interaction with
the interplanetary medium and the solar UV radiation field. A 50-100
times improvement in sensitivity would enable the observation of the
key atmospheric ingredients of Earth-like exoplanets (carbon, oxygen,
ozone), provide crucial input for models of biologically active worlds
outside the solar system, and provide the phenomenological baseline
to understand the Earth atmosphere in context.
---------------------------------------------------------
Title: The PLATO 2.0 mission
Authors: Rauer, H.; Catala, C.; Aerts, C.; Appourchaux, T.; Benz,
W.; Brandeker, A.; Christensen-Dalsgaard, J.; Deleuil, M.; Gizon,
L.; Goupil, M. -J.; Güdel, M.; Janot-Pacheco, E.; Mas-Hesse,
M.; Pagano, I.; Piotto, G.; Pollacco, D.; Santos, Ċ.; Smith, A.;
Suárez, J. -C.; Szabó, R.; Udry, S.; Adibekyan, V.; Alibert, Y.;
Almenara, J. -M.; Amaro-Seoane, P.; Eiff, M. Ammler-von; Asplund, M.;
Antonello, E.; Barnes, S.; Baudin, F.; Belkacem, K.; Bergemann, M.;
Bihain, G.; Birch, A. C.; Bonfils, X.; Boisse, I.; Bonomo, A. S.;
Borsa, F.; Brandão, I. M.; Brocato, E.; Brun, S.; Burleigh, M.;
Burston, R.; Cabrera, J.; Cassisi, S.; Chaplin, W.; Charpinet, S.;
Chiappini, C.; Church, R. P.; Csizmadia, Sz.; Cunha, M.; Damasso, M.;
Davies, M. B.; Deeg, H. J.; Díaz, R. F.; Dreizler, S.; Dreyer, C.;
Eggenberger, P.; Ehrenreich, D.; Eigmüller, P.; Erikson, A.; Farmer,
R.; Feltzing, S.; de Oliveira Fialho, F.; Figueira, P.; Forveille,
T.; Fridlund, M.; García, R. A.; Giommi, P.; Giuffrida, G.; Godolt,
M.; Gomes da Silva, J.; Granzer, T.; Grenfell, J. L.; Grotsch-Noels,
A.; Günther, E.; Haswell, C. A.; Hatzes, A. P.; Hébrard, G.; Hekker,
S.; Helled, R.; Heng, K.; Jenkins, J. M.; Johansen, A.; Khodachenko,
M. L.; Kislyakova, K. G.; Kley, W.; Kolb, U.; Krivova, N.; Kupka, F.;
Lammer, H.; Lanza, A. F.; Lebreton, Y.; Magrin, D.; Marcos-Arenal,
P.; Marrese, P. M.; Marques, J. P.; Martins, J.; Mathis, S.; Mathur,
S.; Messina, S.; Miglio, A.; Montalban, J.; Montalto, M.; Monteiro,
M. J. P. F. G.; Moradi, H.; Moravveji, E.; Mordasini, C.; Morel, T.;
Mortier, A.; Nascimbeni, V.; Nelson, R. P.; Nielsen, M. B.; Noack,
L.; Norton, A. J.; Ofir, A.; Oshagh, M.; Ouazzani, R. -M.; Pápics,
P.; Parro, V. C.; Petit, P.; Plez, B.; Poretti, E.; Quirrenbach, A.;
Ragazzoni, R.; Raimondo, G.; Rainer, M.; Reese, D. R.; Redmer, R.;
Reffert, S.; Rojas-Ayala, B.; Roxburgh, I. W.; Salmon, S.; Santerne,
A.; Schneider, J.; Schou, J.; Schuh, S.; Schunker, H.; Silva-Valio,
A.; Silvotti, R.; Skillen, I.; Snellen, I.; Sohl, F.; Sousa, S. G.;
Sozzetti, A.; Stello, D.; Strassmeier, K. G.; Švanda, M.; Szabó,
Gy. M.; Tkachenko, A.; Valencia, D.; Van Grootel, V.; Vauclair,
S. D.; Ventura, P.; Wagner, F. W.; Walton, N. A.; Weingrill, J.;
Werner, S. C.; Wheatley, P. J.; Zwintz, K.
2014ExA....38..249R Altcode: 2014ExA...tmp...41R; 2013arXiv1310.0696R
PLATO 2.0 has recently been selected for ESA's M3 launch opportunity
(2022/24). Providing accurate key planet parameters (radius, mass,
density and age) in statistical numbers, it addresses fundamental
questions such as: How do planetary systems form and evolve? Are there
other systems with planets like ours, including potentially habitable
planets? The PLATO 2.0 instrument consists of 34 small aperture
telescopes (32 with 25 s readout cadence and 2 with 2.5 s candence)
providing a wide field-of-view (2232 deg <SUP>2</SUP>) and a large
photometric magnitude range (4-16 mag). It focusses on bright (4-11
mag) stars in wide fields to detect and characterize planets down to
Earth-size by photometric transits, whose masses can then be determined
by ground-based radial-velocity follow-up measurements. Asteroseismology
will be performed for these bright stars to obtain highly accurate
stellar parameters, including masses and ages. The combination of
bright targets and asteroseismology results in high accuracy for
the bulk planet parameters: 2 %, 4-10 % and 10 % for planet radii,
masses and ages, respectively. The planned baseline observing strategy
includes two long pointings (2-3 years) to detect and bulk characterize
planets reaching into the habitable zone (HZ) of solar-like stars
and an additional step-and-stare phase to cover in total about 50 %
of the sky. PLATO 2.0 will observe up to 1,000,000 stars and detect
and characterize hundreds of small planets, and thousands of planets
in the Neptune to gas giant regime out to the HZ. It will therefore
provide the first large-scale catalogue of bulk characterized planets
with accurate radii, masses, mean densities and ages. This catalogue
will include terrestrial planets at intermediate orbital distances,
where surface temperatures are moderate. Coverage of this parameter
range with statistical numbers of bulk characterized planets is unique
to PLATO 2.0. The PLATO 2.0 catalogue allows us to e.g.: - complete
our knowledge of planet diversity for low-mass objects, - correlate the
planet mean density-orbital distance distribution with predictions from
planet formation theories,- constrain the influence of planet migration
and scattering on the architecture of multiple systems, and - specify
how planet and system parameters change with host star characteristics,
such as type, metallicity and age. The catalogue will allow us to study
planets and planetary systems at different evolutionary phases. It
will further provide a census for small, low-mass planets. This will
serve to identify objects which retained their primordial hydrogen
atmosphere and in general the typical characteristics of planets
in such low-mass, low-density range. Planets detected by PLATO 2.0
will orbit bright stars and many of them will be targets for future
atmosphere spectroscopy exploring their atmosphere. Furthermore,
the mission has the potential to detect exomoons, planetary rings,
binary and Trojan planets. The planetary science possible with PLATO
2.0 is complemented by its impact on stellar and galactic science via
asteroseismology as well as light curves of all kinds of variable stars,
together with observations of stellar clusters of different ages. This
will allow us to improve stellar models and study stellar activity. A
large number of well-known ages from red giant stars will probe the
structure and evolution of our Galaxy. Asteroseismic ages of bright
stars for different phases of stellar evolution allow calibrating
stellar age-rotation relationships. Together with the results of ESA's
Gaia mission, the results of PLATO 2.0 will provide a huge legacy to
planetary, stellar and galactic science.
---------------------------------------------------------
Title: Filtergraph Calibration for the Polarimetric and Helioseismic
Imager
Authors: Dominguez-Tagle, Carlos; Appourchaux, Thierry; Fourmond,
Jean-Jacques; Philippon, Anne; Le Clec'h, Jean-Christophe; Bouzit,
Mehdi; Le Cocguen, Regis
2014JSAST..12.Tk25D Altcode:
Solar Orbiter mission will study the Sun to the proximity of 0.28 AU,
reaching solar latitudes up to 34°. This spacecraft will be launched
in 2017 and will represent a complete approach to heliophysics. The
Polarimetric and Helioseismic Imager (PHI), on board of Solar Orbiter,
will provide the most important data for helioseismology. PHI will
measure the photospheric vector magnetic field and the line-of-sight
velocity observing the FeI 6173 A absorption line with a narrowband
filtergraph (FG). At different spectral positions, the polarization
state of the incoming light will be analyzed. The FG will provide a
tuning range to compensate the spacecraft radial velocity and to scan
the continuum at both sides of the absorption line. Thus, the fine
tuning of the FG is essential for the instrument performance. Here
we present the FG characterization and calibration status as they
represent an important milestone in the development of the instrument.
---------------------------------------------------------
Title: Optical characterization of the breadboard narrowband
prefilters for Solar Orbiter PHI
Authors: Dominguez-Tagle, Carlos; Appourchaux, Thierry; Ruiz
de Galarreta, Claudia; Fourmond, Jean-Jacques; Philippon, Anne;
Le Clec'h, Jean-Christophe; Bouzit, Mehdi; Bommier, Véronique;
Le Cocguen, Regis; Crussaire, Daniel; Malherbe, Jean-Marie
2014SPIE.9143E..5GD Altcode:
The Polarimetric and Helioseismic Imager (PHI) on board of Solar
Orbiter will observe the Sun to measure the photospheric vector
magnetic field and the line-of-sight velocity. It will employ
a narrowband filtergraph (FG) to scan the FeI 6173 Å absorption
line. At different spectral positions, the polarization state of the
incoming light will be analyzed. The FG will provide a tuning range
to scan the line, the continuum, and to compensate for the spacecraft
radial velocity, as it will approach to the Sun down to 0.28 AU. The
FG includes a Fabry-Perot etalon and two narrowband prefilters. The
bandpass of the narrowest one has a nominal Full Width at Half Maximum
(FWHM) of 2.7 Å. The measurement of the prefilters characteristics is
essential for the instrument calibration. Here we present the results
of the breadboard prefilters characterization, which is an important
milestone in the development of the instrument.
---------------------------------------------------------
Title: Asteroseismic Estimate of Helium Abundance of a Solar Analog
Binary System
Authors: Verma, Kuldeep; Faria, João P.; Antia, H. M.; Basu, Sarbani;
Mazumdar, Anwesh; Monteiro, Mário J. P. F. G.; Appourchaux, Thierry;
Chaplin, William J.; García, Rafael A.; Metcalfe, Travis S.
2014ApJ...790..138V Altcode: 2014arXiv1405.7512V
16 Cyg A and B are among the brightest stars observed by Kepler. What
makes these stars more interesting is that they are solar analogs. 16
Cyg A and B exhibit solar-like oscillations. In this work we use
oscillation frequencies obtained using 2.5 yr of Kepler data to
determine the current helium abundance of these stars. For this we
use the fact that the helium ionization zone leaves a signature on
the oscillation frequencies and that this signature can be calibrated
to determine the helium abundance of that layer. By calibrating the
signature of the helium ionization zone against models of known helium
abundance, the helium abundance in the envelope of 16 Cyg A is found
to lie in the range of 0.231 to 0.251 and that of 16 Cyg B lies in
the range of 0.218 to 0.266.
---------------------------------------------------------
Title: Oscillation mode linewidths and heights of 23 main-sequence
stars observed by Kepler
Authors: Appourchaux, T.; Antia, H. M.; Benomar, O.; Campante, T. L.;
Davies, G. R.; Handberg, R.; Howe, R.; Régulo, C.; Belkacem, K.;
Houdek, G.; García, R. A.; Chaplin, W. J.
2014A&A...566A..20A Altcode: 2014arXiv1403.7046A
Context. Solar-like oscillations have been observed by Kepler and
CoRoT in many solar-type stars, thereby providing a way to probe
the stars using asteroseismology. <BR /> Aims: We provide the mode
linewidths and mode heights of the oscillations of various stars as
a function of frequency and of effective temperature. <BR /> Methods:
We used a time series of nearly two years of data for each star. The
23 stars observed belong to the simple or F-like category. The power
spectra of the 23 main-sequence stars were analysed using both maximum
likelihood estimators and Bayesian estimators, providing individual mode
characteristics such as frequencies, linewidths, and mode heights. We
study the source of systematic errors in the mode linewidths and mode
heights, and we present a way to correct these errors with respect to
a common reference fit. <BR /> Results: Using the correction, we can
explain all sources of systematic errors, which could be reduced to
less than ±15% for mode linewidths and heights, and less than ±5%
for amplitude, when compared to the reference fit. The effect of
a different estimated stellar background and a different estimated
splitting will provide frequency-dependent systematic errors that
might affect the comparison with theoretical mode linewidth and mode
height, therefore affecting the understanding of the physical nature of
these parameters. All other sources of relative systematic errors are
less dependent upon frequency. We also provide the dependence of the
so-called linewidth dip in the middle of the observed frequency range as
a function of effective temperature. We show that the depth of the dip
decreases with increasing effective temperature. The dependence of the
dip on effective temperature may imply that the mixing length parameter
α or the convective flux may increase with effective temperature. <P
/>Tables 4-27 and Appendices are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201323317/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Surface Activity and Oscillation Amplitudes of Red Giants in
Eclipsing Binaries
Authors: Gaulme, P.; Jackiewicz, J.; Appourchaux, T.; Mosser, B.
2014ApJ...785....5G Altcode: 2014arXiv1402.3027G
Among the 19 red-giant stars belonging to eclipsing binary systems
that have been identified in Kepler data, 15 display solar-like
oscillations. We study whether the absence of mode detection in
the remaining 4 is an observational bias or possibly evidence of
mode damping that originates from tidal interactions. A careful
analysis of the corresponding Kepler light curves shows that modes
with amplitudes that are usually observed in red giants would have
been detected if they were present. We observe that mode depletion is
strongly associated with short-period systems, in which stellar radii
account for 16%-24% of the semi-major axis, and where red-giant surface
activity is detected. We suggest that when the rotational and orbital
periods synchronize in close binaries, the red-giant component is spun
up, so that a dynamo mechanism starts and generates a magnetic field,
leading to observable stellar activity. Pressure modes would then be
damped as acoustic waves dissipate in these fields.
---------------------------------------------------------
Title: Seismic analysis of HD 43587Aa, a solar-like oscillator in
a multiple system
Authors: Boumier, P.; Benomar, O.; Baudin, F.; Verner, G.; Appourchaux,
T.; Lebreton, Y.; Gaulme, P.; Chaplin, W.; García, R. A.; Hekker,
S.; Regulo, C.; Salabert, D.; Stahn, T.; Elsworth, Y.; Gizon, L.;
Hall, M.; Mathur, S.; Michel, E.; Morel, T.; Mosser, B.; Poretti,
E.; Rainer, M.; Roxburgh, I.; do Nascimento, J. -D., Jr.; Samadi,
R.; Auvergne, M.; Chaintreuil, S.; Baglin, A.; Catala, C.
2014A&A...564A..34B Altcode: 2014arXiv1402.5053B
Context. The object HD 43587Aa is a G0V star observed during the
145-day LRa03 run of the COnvection, ROtation and planetary Transits
space mission (CoRoT), for which complementary High Accuracy Radial
velocity Planet Searcher (HARPS) spectra with S/N > 300 were also
obtained. Its visual magnitude is 5.71, and its effective temperature is
close to 5950 K. It has a known companion in a highly eccentric orbit
and is also coupled with two more distant companions. <BR /> Aims:
We undertake a preliminary investigation of the internal structure
of HD 43587Aa. <BR /> Methods: We carried out a seismic analysis of
the star, using maximum likelihood estimators and Markov chain Monte
Carlo methods. <BR /> Results: We established the first table of the
eigenmode frequencies, widths, and heights for HD 43587Aa. The star
appears to have a mass and a radius slightly larger than the Sun, and is
slightly older (5.6 Gyr). Two scenarios are suggested for the geometry
of the star: either its inclination angle is very low, or the rotation
velocity of the star is very low. <BR /> Conclusions: A more detailed
study of the rotation and of the magnetic and chromospheric activity for
this star is needed, and will be the subject of a further study. New
high resolution spectrometric observations should be performed for at
least several months in duration.
---------------------------------------------------------
Title: Seismic constraints on the radial dependence of the internal
rotation profiles of six Kepler subgiants and young red giants
Authors: Deheuvels, S.; Doğan, G.; Goupil, M. J.; Appourchaux, T.;
Benomar, O.; Bruntt, H.; Campante, T. L.; Casagrande, L.; Ceillier,
T.; Davies, G. R.; De Cat, P.; Fu, J. N.; García, R. A.; Lobel,
A.; Mosser, B.; Reese, D. R.; Regulo, C.; Schou, J.; Stahn, T.;
Thygesen, A. O.; Yang, X. H.; Chaplin, W. J.; Christensen-Dalsgaard,
J.; Eggenberger, P.; Gizon, L.; Mathis, S.; Molenda-Żakowicz, J.;
Pinsonneault, M.
2014A&A...564A..27D Altcode: 2014arXiv1401.3096D
Context. We still do not understand which physical mechanisms are
responsible for the transport of angular momentum inside stars. The
recent detection of mixed modes that contain the clear signature of
rotation in the spectra of Kepler subgiants and red giants gives us
the opportunity to make progress on this question. <BR /> Aims: Our
aim is to probe the radial dependence of the rotation profiles for a
sample of Kepler targets. For this purpose, subgiants and early red
giants are particularly interesting targets because their rotational
splittings are more sensitive to the rotation outside the deeper core
than is the case for their more evolved counterparts. <BR /> Methods:
We first extracted the rotational splittings and frequencies of the
modes for six young Kepler red giants. We then performed a seismic
modeling of these stars using the evolutionary codes Cesam2k and
astec. By using the observed splittings and the rotational kernels
of the optimal models, we inverted the internal rotation profiles
of the six stars. <BR /> Results: We obtain estimates of the core
rotation rates for these stars, and upper limits to the rotation in
their convective envelope. We show that the rotation contrast between
the core and the envelope increases during the subgiant branch. Our
results also suggest that the core of subgiants spins up with time,
while their envelope spins down. For two of the stars, we show that a
discontinuous rotation profile with a deep discontinuity reproduces
the observed splittings significantly better than a smooth rotation
profile. Interestingly, the depths that are found to be most probable
for the discontinuities roughly coincide with the location of the
H-burning shell, which separates the layers that contract from those
that expand. <BR /> Conclusions: We characterized the differential
rotation pattern of six young giants with a range of metallicities, and
with both radiative and convective cores on the main sequence. This will
bring observational constraints to the scenarios of angular momentum
transport in stars. Moreover, if the existence of sharp gradients in
the rotation profiles of young red giants is confirmed, it is expected
to help in distinguishing between the physical processes that could
transport angular momentum in the subgiant and red giant branches. <P
/>Appendices and Tables 3-9 are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201322779/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: The PLATO 2.0 Mission
Authors: Pagano, I.; Rauer, H.; Aerts, C.; Appourchaux, T.; Benz,
W.; Brandeker, A.; Christensen-Dalsgaard, J.; Deleuil, M.; Gizon, L.;
Goupil, M. -J.; Guedel, M.; Heras, A.; Janot-Pacheco, E.; Mas-Hesse,
M.; Piotto, G.; Pollaco, D.; Ragazzoni, R.; Santos, N. C.; Smith,
A.; Suarez, J. C.; Szabo, R.; Udry, S.
2014EPSC....9..789P Altcode:
PLATO 2.0 is the M class mission selected by ESA for its M3 launch
slot in the framework of the Cosmic Vision 2015-2025 program. The main
goals of PLATO 2.0 are the detection of terrestrial exoplanets in the
habitable zone of solar-type stars and the characterization of their
bulk properties needed to determine their habitability. Moreover,
PLATO 2.0 will be key in understanding the formation, architecture,
and evolution of planetary systems thanks to a thorough inventory
of the physical properties of thousands of rocky, icy, and gaseous
giant planets. We will illustrate the PLATO 2.0 science goals, how
the instrument is conceived to fulfil the science requirements, and
how the project is organized to implement the instrument, plan the
observations, and exploit the resulting data.
---------------------------------------------------------
Title: Prospects for Detecting Asteroseismic Binaries in Kepler Data
Authors: Miglio, A.; Chaplin, W. J.; Farmer, R.; Kolb, U.; Girardi,
L.; Elsworth, Y.; Appourchaux, T.; Handberg, R.
2014ApJ...784L...3M Altcode: 2014arXiv1402.2480M
Asteroseismology may in principle be used to detect unresolved stellar
binary systems comprised of solar-type stars and/or red giants. This
novel method relies on the detection of the presence of two solar-like
oscillation spectra in the frequency spectrum of a single light
curve. Here, we make predictions of the numbers of systems that may be
detectable in data already collected by the NASA Kepler Mission. Our
predictions, which are based upon TRILEGAL and BiSEPS simulations
of the Kepler field of view, indicate that as many as 200 or more
"asteroseismic binaries" may be detectable in this manner. Most
of these binaries should be comprised of two He-core-burning red
giants. Owing largely to the limited numbers of targets with the
requisite short-cadence Kepler data, we expect only a small number of
detected binaries containing solar-type stars. The predicted yield of
detections is sensitive to the assumed initial mass ratio distribution
(IMRD) of the binary components and therefore represents a sensitive
calibration of the much debated IMRD near mass ratio unity.
---------------------------------------------------------
Title: A crash course on data analysis in asteroseismology
Authors: Appourchaux, Thierry
2014aste.book..123A Altcode: 2011arXiv1103.5352A
In this course, I try to provide a few basics required for performing
data analysis in asteroseismology. First, I address how one can properly
treat times series: the sampling, the filtering effect, the use of
Fourier transform, the associated statistics. Second, I address how one
can apply statistics for decision making and for parameter estimation
either in a frequentist of a Bayesian framework. Last, I review how
these basic principle have been applied (or not) in asteroseismology.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Asteroseismic study of solar-type
stars (Chaplin+, 2014)
Authors: Chaplin, W. J.; Basu, S.; Huber, D.; Serenelli, A.;
Casagrande, L.; Silva Aguirre, V.; Ball, W. H.; Creevey, O. L.;
Gizon, L.; Handberg, R.; Karoff, C.; Lutz, R.; Marques, J. P.;
Miglio, A.; Stello, D.; Suran, M. D.; Pricopi, D.; Metcalfe, T. S.;
Monteiro, M. J. P. F. G.; Molenda-Zakowicz, J.; Appourchaux, T.;
Christensen-Dalsgaard, J.; Elsworth, Y.; Garcia, R. A.; Houdek, G.;
Kjeldsen, H.; Bonanno, A.; Campante, T. L.; Corsaro, E.; Gaulme, P.;
Hekker, S.; Mathur, S.; Mosser, B.; Regulo, C.; Salabert, D.
2014yCat..22100001C Altcode:
During the first 10 months of science operations more than 2000
solar-type stars were selected by the Kepler Asteroseismic Science
Consortium (KASC) to be observed as part of an asteroseismic survey
of the Sun-like population in the Kepler field of view. Solar-like
oscillations were detected by Kepler in more than 500 stars (Chaplin
et al. 2011Sci...332..213C), and from these data robust global or
average asteroseismic parameters were determined for all targets in the
sample. These asteroseismic parameters allow us to estimate fundamental
properties of the stars. In this paper we present stellar properties
- namely masses, radii, surface gravities, mean densities and ages -
of this asteroseismic sample of main-sequence and subgiant stars. <P
/>(5 data files).
---------------------------------------------------------
Title: Asteroseismic Fundamental Properties of Solar-type Stars
Observed by the NASA Kepler Mission
Authors: Chaplin, W. J.; Basu, S.; Huber, D.; Serenelli, A.;
Casagrande, L.; Silva Aguirre, V.; Ball, W. H.; Creevey, O. L.;
Gizon, L.; Handberg, R.; Karoff, C.; Lutz, R.; Marques, J. P.;
Miglio, A.; Stello, D.; Suran, M. D.; Pricopi, D.; Metcalfe, T. S.;
Monteiro, M. J. P. F. G.; Molenda-Żakowicz, J.; Appourchaux, T.;
Christensen-Dalsgaard, J.; Elsworth, Y.; García, R. A.; Houdek, G.;
Kjeldsen, H.; Bonanno, A.; Campante, T. L.; Corsaro, E.; Gaulme, P.;
Hekker, S.; Mathur, S.; Mosser, B.; Régulo, C.; Salabert, D.
2014ApJS..210....1C Altcode: 2013arXiv1310.4001C
We use asteroseismic data obtained by the NASA Kepler mission to
estimate the fundamental properties of more than 500 main-sequence and
sub-giant stars. Data obtained during the first 10 months of Kepler
science operations were used for this work, when these solar-type
targets were observed for one month each in survey mode. Stellar
properties have been estimated using two global asteroseismic parameters
and complementary photometric and spectroscopic data. Homogeneous sets
of effective temperatures, T <SUB>eff</SUB>, were available for the
entire ensemble from complementary photometry; spectroscopic estimates
of T <SUB>eff</SUB> and [Fe/H] were available from a homogeneous
analysis of ground-based data on a subset of 87 stars. We adopt
a grid-based analysis, coupling six pipeline codes to 11 stellar
evolutionary grids. Through use of these different grid-pipeline
combinations we allow implicitly for the impact on the results of
stellar model dependencies from commonly used grids, and differences
in adopted pipeline methodologies. By using just two global parameters
as the seismic inputs we are able to perform a homogenous analysis
of all solar-type stars in the asteroseismic cohort, including many
targets for which it would not be possible to provide robust estimates
of individual oscillation frequencies (due to a combination of low
signal-to-noise ratio and short dataset lengths). The median final
quoted uncertainties from consolidation of the grid-based analyses
are for the full ensemble (spectroscopic subset) approximately 10.8%
(5.4%) in mass, 4.4% (2.2%) in radius, 0.017 dex (0.010 dex) in log g,
and 4.3% (2.8%) in mean density. Around 36% (57%) of the stars have
final age uncertainties smaller than 1 Gyr. These ages will be useful
for ensemble studies, but should be treated carefully on a star-by-star
basis. Future analyses using individual oscillation frequencies will
offer significant improvements on up to 150 stars, in particular for
estimates of the ages, where having the individual frequency data is
most important.
---------------------------------------------------------
Title: On the development of a Fourier Transform Spectrometer for
Solar Physics
Authors: Ruiz de Galarreta, Claudia; Vial, Jean-Claude; Appourchaux,
Thierry; Philippon, Anne
2014cosp...40E2793R Altcode:
The origin and the evolution of the different structures that inhabit
beyond the Sun’s photosphere, as well as the processes involved in
the dynamics and the heating of the corona remain quite unknown. The
inextricable complexity of the physical phenomena that govern the solar
outer atmosphere is accompanied by the lack of suitable data adapted to
the scientific need. Indeed, the interpretation and the models of the
mechanisms that connect the exchanges between the chromosphere and the
corona depend on critical observational parameters. It is for example
essential to measure broad bands of vertical temperature and density
ranges that fit the multiple spatial and temporal scales that are
characteristic of the different events that take place in the Sun. The
understanding of the dynamics of the plasma must be also based on the
Doppler analysis of the observed scene. That implies the ability to
combine time resolved spectroscopic and imaging technologies. Moreover,
space is the place to observe the far UV corona and that implies a
real technical challenge. Despite excellent advances in technology and
instrumentation, the study of the Sun in the far UV is a fairly recent
science. To date, no solar space mission could provide a combined and
simultaneous diagnostic of both observables in the spectral range of
interest. It is because of these expectations that the study of a
new device called IFTSUV (the acronym of Imaging Fourier Transform
Spectrometer working in the far UV) is presented in this paper. We
start from the definition of the scientific requirements that lead to
the technical choice, the first objective of this study is to develop
a preliminary instrumental model of the IFTSUV. The overall technical
and design specifications are based in theoretical calculations that
have been expressed in terms of spectral accuracy, image quality and
signal to noise ratio. Throughout the identification of difficult
points, the realization of a servo-metrology system to control the
sampling mirror appears naturally as an intrinsic need of proof of
concept. Indeed, the wavenumbers from the raw spectra are set by the
interferogram. That implies that acquisition must be rigorously constant
and that the sampling steps must be known with high accuracy. Therefore,
the mockup of a metrological solution that has been developped at IAS
will is also presented. The results on the damonstrator that validate
and converge to the optimization and prototyping of a system that could
be integrated in a space based application will be discussed. Finally we
propose a discussion on the possible future space mission opportunities
in which this innovative project could be framed.
---------------------------------------------------------
Title: The History of the g-mode Quest
Authors: Appourchaux, T.; Pallé, P. L.
2013ASPC..478..125A Altcode: 2013arXiv1309.3835A
The quest for the solar gravity modes (or g modes) is key for the
understanding of the structure and dynamics of the solar core. We
review the history of the solar g-mode searches which is separated in
three nearly distinct eras which correspond to: the theory of g modes,
the search from the ground and the search from space. The prospects
of definitive solar g-mode detection are also discussed.
---------------------------------------------------------
Title: The JOVIAL Project for Jovian Seismology
Authors: Schmider, F. X.; Appourchaux, T.; Gaulme, P.; Guillot, T.;
Sato, B.; Murphy, N.; Daban, J. B.; Gay, J.; Soulat, L.; Baudin,
F.; Boumier, P.; Ollivier, M.; Bordé. P.; Jackiewicz, J.; Ida, S.;
Showman, A. P.
2013ASPC..478..119S Altcode:
Jovian seismology is a unique tool to determine the internal structure
of the giant planet. It could uncover the size and mass of the core,
if any, the existence of a “plasma phase transition” between the
molecular and the metallic hydrogen envelope, reveal the internal
dynamic, and more generally address the formation and evolution of
giant planets in the solar system giving a point of comparison for extra
solar planets. Jovian seismology requires special observing tool. SYMPA
(Schmider et al. 2007; Gaulme et al. 2008) was the first project
specially designed for those objectives. A new type of instrument,
a Doppler Imager, had been developed. The project permitted for the
first time the measurement of the fundamental acoustic frequency
of Jupiter (Gaulme et al. 2011). It also validated the principle
of the instrument. However, several limitations appeared during the
observations. The main one was the poor temporal coverage. A new version
of the Doppler Spectro Imager (DSI) has been studied extensively in
the framework of the development of a space instrument for the JUICE
mission. A prototype of this new device is presently developed in the
laboratory (Soulat et al. 2011) and shows excellent sensitivity and
stability. It will be tested on the sky in January 2014. The JOVIAL
project foresees the installation of three similar instruments on
three telescopes around the Earth (Japan, France, and USA) that will
provide the necessary continuity in the observations. We expect to
observe winds in the Jovian atmosphere with a precision better than
2 m/s and to detect modes with amplitude as low as 5 cm/s up to the
degree ℓ = 10 at least. The main objective of the project is the
detection of the Jovian core.
---------------------------------------------------------
Title: Asteroseismology observations and space missions
Authors: Appourchaux, T.; Grundahl, F.
2013arXiv1312.6993A Altcode:
Contribution to a book entitled "Extraterrestrial seismology".
---------------------------------------------------------
Title: Mode Line Widths in Red-Giant Stars
Authors: Baudin, F.; Elsworth, Y.; Hekker, S.; Kallinger, T.; Stello,
D.; Mosser, B.; Appourchaux, T.; Belkacem, K.; Benomar, O.; Barban,
C.; Chaplin, W. J.
2013ASPC..479..179B Altcode:
Mode line widths and amplitudes provide valuable information on stellar
oscillation excitation and damping, and thus on physical processes such
as convection, radiative losses and convection/pulsation coupling. We
present preliminary results for mode line widths obtained by fitting
mode spectra from Kepler observations. The difficulties of such fitting
are discussed as well as these preliminary estimates in the context
of models.
---------------------------------------------------------
Title: Kepler White Paper: Asteroseismology of Solar-Like Oscillators
in a 2-Wheel Mission
Authors: Chaplin, W. J; Kjeldsen, H.; Christensen-Dalsgaard, J.;
Gilliland, R. L.; Kawaler, S. D.; Basu, S.; De Ridder, J.; Huber, D.;
Arentoft, T.; Schou, J.; Garcia, R. A.; Metcalfe, T. S.; Brogaard, K.;
Campante, T. L.; Elsworth, Y.; Miglio, A.; Appourchaux, T.; Bedding,
T. R.; Hekker, S.; Houdek, G.; Karoff, C.; Molenda-Zakowicz, J.;
Monteiro, M. J. P. F. G.; Silva Aguirre, V.; Stello, D.; Ball, W.;
Beck, P. G.; Birch, A. C.; Buzasi, D. L.; Casagrande, L.; Cellier,
T.; Corsaro, E.; Creevey, O. L.; Davies, G. R.; Deheuvels, S.; Dogan,
G.; Gizon, L.; Grundahl, F.; Guzik, J.; Handberg, R.; Jimenez, A.;
Kallinger, T.; Lund, M. N.; Lundkvist, M.; Mathis, S.; Mathur, S.;
Mazumdar, A.; Mosser, B.; Neiner, C.; Nielsen, M. B.; Palle, P. L.;
Pinsonneault, M. H.; Salabert, D.; Serenelli, A. M.; Shunker, H.;
White, T. R.
2013arXiv1309.0702C Altcode:
We comment on the potential for continuing asteroseismology of
solar-type and red-giant stars in a 2-wheel Kepler Mission. Our main
conclusion is that by targeting stars in the ecliptic it should be
possible to perform high-quality asteroseismology, as long as favorable
scenarios for 2-wheel pointing performance are met. Targeting the
ecliptic would potentially facilitate unique science that was not
possible in the nominal Mission, notably from the study of clusters
that are significantly brighter than those in the Kepler field. Our
conclusions are based on predictions of 2-wheel observations made by
a space photometry simulator, with information provided by the Kepler
Project used as input to describe the degraded pointing scenarios. We
find that elevated levels of frequency-dependent noise, consistent with
the above scenarios, would have a significant negative impact on our
ability to continue asteroseismic studies of solar-like oscillators in
the Kepler field. However, the situation may be much more optimistic
for observations in the ecliptic, provided that pointing resets of the
spacecraft during regular desaturations of the two functioning reaction
wheels are accurate at the < 1 arcsec level. This would make it
possible to apply a post-hoc analysis that would recover most of the
lost photometric precision. Without this post-hoc correction---and the
accurate re-pointing it requires---the performance would probably be
as poor as in the Kepler-field case. Critical to our conclusions for
both fields is the assumed level of pointing noise (in the short-term
jitter and the longer-term drift). We suggest that further tests will
be needed to clarify our results once more detail and data on the
expected pointing performance becomes available, and we offer our
assistance in this work.
---------------------------------------------------------
Title: Seismic constraints on rotation of Sun-like star and mass
of exoplanet
Authors: Gizon, L.; Ballot, J.; Michel, E.; Stahn, T.; Vauclair, G.;
Bruntt, H.; Quirion, P. -O.; Benomar, O.; Vauclair, S.; Appourchaux,
T.; Auvergne, M.; Baglin, A.; Barban, C.; Baudin, F.; Bazot, M.;
Campante, T.; Catala, C.; Chaplin, W.; Creevey, O.; Deheuvels, S.;
Dolez, N.; Elsworth, Y.; Garcia, R.; Gaulme, P.; Mathis, S.; Mathur,
S.; Mosser, B.; Regulo, C.; Roxburgh, I.; Salabert, D.; Samadi, R.;
Sato, K.; Verner, G.; Hanasoge, S.; Sreenivasan, K. R.
2013PNAS..11013267G Altcode: 2013arXiv1308.4352G
Rotation is thought to drive cyclic magnetic activity in the Sun
and Sun-like stars. Stellar dynamos, however, are poorly understood
owing to the scarcity of observations of rotation and magnetic fields
in stars. Here, inferences are drawn on the internal rotation of a
distant Sun-like star by studying its global modes of oscillation. We
report asteroseismic constraints imposed on the rotation rate and the
inclination of the spin axis of the Sun-like star HD 52265, a principal
target observed by the CoRoT satellite that is known to host a planetary
companion. These seismic inferences are remarkably consistent with an
independent spectroscopic observation (rotational line broadening)
and with the observed rotation period of star spots. Furthermore,
asteroseismology constrains the mass of exoplanet HD 52265b. Under
the standard assumption that the stellar spin axis and the axis of the
planetary orbit coincide, the minimum spectroscopic mass of the planet
can be converted into a true mass of 1.85 (+0.52,-0.42) M_Jupiter,
which implies that it is a planet, not a brown dwarf.
---------------------------------------------------------
Title: Filtergraph Calibration for the Polarimetric and Helioseismic
Imager
Authors: Dominguez-Tagle, Carlos; Appourchaux, Thierry; Fourmond,
Jean-Jacques; Philippon, Anne; Le Clec'h, Jean-Christophe; Bouzit,
Mehdi; Le Cocguen, Regis
2013ists.conf...46D Altcode:
ESA's Solar Orbiter mission will study the Sun to the proximity
of 0.28 AU, reaching solar latitudes up to 34deg. This spacecraft
will be launched in 2017 and will represent a complete approach
to heliophysics. The Polarimetric and Helioseismic Imager (PHI),
on board of Solar Orbiter, will provide the most important data for
helioseismology. PHI will measure the photospheric vector magnetic field
and the line-of-sight velocity observing the FeI 6173A absorption line
with a narrowband filtergraph (FG). At different spectral positions,
the polarisation state of the incoming light will be analysed. The FG
will provide a tuning range to compensate the spacecraft radial velocity
and to scan the continuum at both sides the absorption line. Thus, the
fine tuning of the FG is essential for the instrument performance. Here
we present the FG characterisation and calibration status as they
represent an important milestone in the development of the instrument.
---------------------------------------------------------
Title: Helioseismology with PICARD
Authors: Corbard, T.; Salabert, D.; Boumier, P.; Appourchaux, T.;
Hauchecorne, A.; Journoud, P.; Nunge, A.; Gelly, B.; Hochedez, J. F.;
Irbah, A.; Meftah, M.; Renaud, C.; Turck-Chièze, S.
2013JPhCS.440a2025C Altcode: 2013arXiv1301.6940C
PICARD is a CNES micro-satellite launched in June 2010 [17]. Its main
goal is to measure the solar shape, total and spectral irradiance during
the ascending phase of the activity cycle. The SODISM telescope onboard
PICARD also allows us to conduct a program for helioseismology in
intensity at 535.7 nm [5]. One-minute cadence low-resolution full images
are available for a so-called medium-l program, and high-resolution
images of the limb recorded every 2 minutes are used to study mode
amplification near the limb in the perspective of g-mode search. First
analyses and results from these two programs are presented here.
---------------------------------------------------------
Title: Stellar Ages and Convective Cores in Field Main-sequence Stars:
First Asteroseismic Application to Two Kepler Targets
Authors: Silva Aguirre, V.; Basu, S.; Brandão, I. M.;
Christensen-Dalsgaard, J.; Deheuvels, S.; Doğan, G.; Metcalfe, T. S.;
Serenelli, A. M.; Ballot, J.; Chaplin, W. J.; Cunha, M. S.; Weiss,
A.; Appourchaux, T.; Casagrande, L.; Cassisi, S.; Creevey, O. L.;
García, R. A.; Lebreton, Y.; Noels, A.; Sousa, S. G.; Stello, D.;
White, T. R.; Kawaler, S. D.; Kjeldsen, H.
2013ApJ...769..141S Altcode: 2013arXiv1304.2772S
Using asteroseismic data and stellar evolution models we obtain the
first detection of a convective core in a Kepler field main-sequence
star, putting a stringent constraint on the total size of the mixed
zone and showing that extra mixing beyond the formal convective
boundary exists. In a slightly less massive target the presence of
a convective core cannot be conclusively discarded, and thus its
remaining main-sequence lifetime is uncertain. Our results reveal
that best-fit models found solely by matching individual frequencies
of oscillations corrected for surface effects do not always properly
reproduce frequency combinations. Moreover, slightly different criteria
to define what the best-fit model is can lead to solutions with similar
global properties but very different interior structures. We argue that
the use of frequency ratios is a more reliable way to obtain accurate
stellar parameters, and show that our analysis in field main-sequence
stars can yield an overall precision of 1.5%, 4%, and 10% in radius,
mass, and age, respectively. We compare our results with those obtained
from global oscillation properties, and discuss the possible sources of
uncertainties in asteroseismic stellar modeling where further studies
are still needed.
---------------------------------------------------------
Title: Mode lifetime and associated scaling relations
Authors: Belkacem, K.; Appourchaux, T.; Baudin, F.; Dupret, M. A.;
Goupil, M. J.; Marques, J. P.; Noels, A.; Samadi, R.
2013EPJWC..4303009B Altcode:
Thanks to the CoRoT and Kepler spacecrafts, scaling relations (linking
seismic indices and global stellar parameters) are becoming the
cornerstone of ensemble asteroseismology. Among them, the relation
between the cut-off frequency and the frequency of the maximum in
the power spectrum of solar-like pulsators as well as the relation
between mode lifetime and the effective temperature remain poorly
understood. However, a solid theoretical background is essential
to assess the accuracy of those relations and subsequently of the
derived stellar parameters. We will thus present recent advances on the
understanding of the underlying mechanisms governing those relations
and show that the physics of mode lifetime (thus of mode damping)
plays a major role.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Abundances of 93 solar-type Kepler
targets (Bruntt+, 2012)
Authors: Bruntt, H.; Basu, S.; Smalley, B.; Chaplin, W. J.; Verner,
G. A.; Bedding, T. R.; Catala, C.; Gazzano, J. -C.; Molenda-Zakowicz,
J.; Thygesen, A. O.; Uytterhoeven, K.; Hekker, S.; Huber, D.; Karoff,
C.; Mathur, S.; Mosser, B.; Appourchaux, T.; Campante, T. L.; Elsworth,
Y.; Garcia, R. A.; Handberg, R.; Metcalfe, T. S.; Quirion, P. -O.;
Regulo, C.; Roxburgh, I. W.; Stello, D.; Christensen-Dalsgaard,
J.; Kawaler, S. D.; Kjeldsen, H.; Morris, R. L.; Quintana, E. V.;
Sanderfer, D. T.
2013yCat..74230122B Altcode:
The spectra were obtained with the ESPaDOnS spectrograph at the 3.6-m
Canada-France-Hawaii Telescope (CFHT) in USA and with the NARVAL
spectrograph mounted on the 2-m Bernard Lyot Telescope at the Pic du
Midi Observatory in France. In both the facilities, the observations
were carried out as service observations from May to September in
2010. <P />(3 data files).
---------------------------------------------------------
Title: Metrology for a solar imaging Fourier transform spectrometer
working in the far UV: from the instrumental concept to the first
experimental results
Authors: Ruiz de Galarreta Fanjul, C.; Bouzit, M.; Appourchaux, T.;
Dassas, K.; Viale, T.; Philippon, A.; Vial, J. -C.; Maillard, J. -P.
2012SPIE.8450E..0DR Altcode:
The spectroscopy of the far UV emission lines of the solar spectrum
combined with an imaging capability is essential to understand the
physics of the outer solar atmosphere. An imaging Fourier transform
spectrometer (IFTSUV) is an attractive instrumental solution to perform
such far-UV solar observations. Working in the far UV involves high
precision metrology to maintain the optical path difference (OPD) during
the entire scanning process of the interferogram. It also involves
a compact all-reflection design for UV applications. We present
the specification of a servo-system that enables dynamic tip/tilt
alignment compensation and OPD sampling measurement of the IFTSUV
scanning mirror. We also discuss the first experimental results of a
breadboard as well as the preliminary design of a space-based device.
---------------------------------------------------------
Title: Echoes: a new instrumental concept of spectro-imaging for
Jovian seismology
Authors: Soulat, L.; Schmider, F. -X.; Robbe-Dubois, S.; Appourchaux,
T.; Bresson, Y.; Daban, J. -B.; Gaulme, P.; Gay, J.; Gouvret, C.
2012SPIE.8442E..4MS Altcode:
Echoes is a project of a space-borne instrument which has been proposed
as part of the JUICE mission which is selected in the Cosmic Vision
program of the European Space Agency (ESA) to perform seismic and
dynamics studies of Jupiter's interior and atmosphere. Based on an
original Mach-Zehnder design, the instrument aims to measure Doppler
shifts of solar spectral lines, which are reflected by cloud layers
of Jupiter's upper troposphere, coupled with imaging capabilities. It
is specified to detect global oscillations with degree up to l = 50
and amplitude as low as 1 cm/s at the surface of Jupiter. In order
to check the compliance of the instrument, and its capability to
operate in representative environment (TRL5), we build a prototype to
perform tests. In this paper, we present the prototype implemented
at Observatoire de la Côte d'Azur in collaboration with Institut
d'Astrophysique Spatiale. We describe the design of the Mach-Zehnder
and the procedure of control and adjustment. We present the necessary
tests and we show on simulation that the measurements will provide
the required precision. In conclusion, we will explain the perspective
for such a new instrument.
---------------------------------------------------------
Title: Seismic Analysis of Four Solar-like Stars Observed during
More Than Eight Months by Kepler
Authors: Mathur, S.; Campante, T. L.; Handberg, R.; García, R. A.;
Appourchaux, T.; Bedding, T. R.; Mosser, B.; Chaplin, W. J.; Ballot,
J.; Benomar, O.; Bonanno, A.; Corsaro, E.; Gaulme, P.; Hekker,
S.; Régulo, C.; Salabert, D.; Verner, G.; White, T. R.; Brandão,
I. M.; Creevey, O. L.; Dogan, G.; Bazot, M.; Cunha, M. S.; Elsworth,
Y.; Huber, D.; Hale, S. J.; Houdek, G.; Karoff, C.; Lundkvist, M.;
Metcalfe, T. S.; Molenda-Zakowicz, J.; Monteiro, M. J. P. F. G.;
Thompson, M. J.; Stello, D.; Christensen-Dalsgaard, J.; Gilliland,
R. L.; Kawaler, S. D.; Kjeldsen, H.; Clarke, B. D.; Girouard, F. R.;
Hall, J. R.; Quintana, E. V.; Sanderfer, D. T.; Seader, S. E.
2012ASPC..462..180M Altcode: 2011arXiv1110.0135M
Having started science operations in May 2009, the Kepler photometer
has been able to provide exquisite data for solar-like stars. Five
out of the 42 stars observed continuously during the survey phase
show evidence of oscillations, even though they are rather faint
(magnitudes from 10.5 to 12). In this paper, we present an overview
of the results of the seismic analysis of 4 of these stars observed
during more than eight months.
---------------------------------------------------------
Title: The EUI instrument on board the Solar Orbiter mission: from
breadboard and prototypes to instrument model validation
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Appourchaux, T.;
Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Auchère, F.;
Zhukov, A.; Dumesnil, C.; Delmotte, F.; Kennedy, T.; Mercier, R.;
Pfiffner, D.; Rossi, L.; Tandy, J.; BenMoussa, A.; Smith, P.
2012SPIE.8443E..07H Altcode:
The Solar Orbiter mission will explore the connection between the Sun
and its heliosphere, taking advantage of an orbit approaching the Sun at
0.28 AU. As part of this mission, the Extreme Ultraviolet Imager (EUI)
will provide full-sun and high-resolution image sequences of the solar
atmosphere at selected spectral emission lines in the extreme and vacuum
ultraviolet. To achieve the required scientific performances under the
challenging constraints of the Solar Orbiter mission it was required
to further develop existing technologies. As part of this development,
and of its maturation of technology readiness, a set of breadboard and
prototypes of critical subsystems have thus been realized to improve
the overall instrument design. The EUI instrument architecture, its
major components and sub-systems are described with their driving
constraints and the expected performances based on the breadboard and
prototype results. The instrument verification and qualification plan
will also be discussed. We present the thermal and mechanical model
validation, the instrument test campaign with the structural-thermal
model (STM), followed by the other instrument models in advance of
the flight instrument manufacturing and AIT campaign.
---------------------------------------------------------
Title: Seismic Evidence for a Rapidly Rotating Core in a
Lower-giant-branch Star Observed with Kepler
Authors: Deheuvels, S.; García, R. A.; Chaplin, W. J.; Basu, S.;
Antia, H. M.; Appourchaux, T.; Benomar, O.; Davies, G. R.; Elsworth,
Y.; Gizon, L.; Goupil, M. J.; Reese, D. R.; Regulo, C.; Schou, J.;
Stahn, T.; Casagrande, L.; Christensen-Dalsgaard, J.; Fischer, D.;
Hekker, S.; Kjeldsen, H.; Mathur, S.; Mosser, B.; Pinsonneault, M.;
Valenti, J.; Christiansen, J. L.; Kinemuchi, K.; Mullally, F.
2012ApJ...756...19D Altcode: 2012arXiv1206.3312D
Rotation is expected to have an important influence on the structure
and the evolution of stars. However, the mechanisms of angular momentum
transport in stars remain theoretically uncertain and very complex to
take into account in stellar models. To achieve a better understanding
of these processes, we desperately need observational constraints on the
internal rotation of stars, which until very recently was restricted to
the Sun. In this paper, we report the detection of mixed modes—i.e.,
modes that behave both as g modes in the core and as p modes in
the envelope—in the spectrum of the early red giant KIC 7341231,
which was observed during one year with the Kepler spacecraft. By
performing an analysis of the oscillation spectrum of the star, we
show that its non-radial modes are clearly split by stellar rotation
and we are able to determine precisely the rotational splittings of
18 modes. We then find a stellar model that reproduces very well the
observed atmospheric and seismic properties of the star. We use this
model to perform inversions of the internal rotation profile of the
star, which enables us to show that the core of the star is rotating at
least five times faster than the envelope. This will shed new light on
the processes of transport of angular momentum in stars. In particular,
this result can be used to place constraints on the angular momentum
coupling between the core and the envelope of early red giants, which
could help us discriminate between the theories that have been proposed
over the last few decades.
---------------------------------------------------------
Title: Oscillation mode frequencies of 61 main-sequence and subgiant
stars observed by Kepler
Authors: Appourchaux, T.; Chaplin, W. J.; García, R. A.; Gruberbauer,
M.; Verner, G. A.; Antia, H. M.; Benomar, O.; Campante, T. L.; Davies,
G. R.; Deheuvels, S.; Handberg, R.; Hekker, S.; Howe, R.; Régulo,
C.; Salabert, D.; Bedding, T. R.; White, T. R.; Ballot, J.; Mathur,
S.; Silva Aguirre, V.; Elsworth, Y. P.; Basu, S.; Gilliland, R. L.;
Christensen-Dalsgaard, J.; Kjeldsen, H.; Uddin, K.; Stumpe, M. C.;
Barclay, T.
2012A&A...543A..54A Altcode: 2012arXiv1204.3147A
Context. Solar-like oscillations have been observed by Kepler and CoRoT
in several solar-type stars, thereby providing a way to probe the stars
using asteroseismology <BR /> Aims: We provide the mode frequencies of
the oscillations of various stars required to perform a comparison with
those obtained from stellar modelling. <BR /> Methods: We used a time
series of nine months of data for each star. The 61 stars observed were
categorised in three groups: simple, F-like, and mixed-mode. The simple
group includes stars for which the identification of the mode degree is
obvious. The F-like group includes stars for which the identification
of the degree is ambiguous. The mixed-mode group includes evolved stars
for which the modes do not follow the asymptotic relation of low-degree
frequencies. Following this categorisation, the power spectra of the
61 main-sequence and subgiant stars were analysed using both maximum
likelihood estimators and Bayesian estimators, providing individual mode
characteristics such as frequencies, linewidths, and mode heights. We
developed and describe a methodology for extracting a single set of
mode frequencies from multiple sets derived by different methods and
individual scientists. We report on how one can assess the quality of
the fitted parameters using the likelihood ratio test and the posterior
probabilities. <BR /> Results: We provide the mode frequencies of
61 stars (with their 1-σ error bars), as well as their associated
échelle diagrams. <P />Appendices are available in electronic form
at <A href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Accurate fundamental parameters and detailed abundance patterns
from spectroscopy of 93 solar-type Kepler targets
Authors: Bruntt, H.; Basu, S.; Smalley, B.; Chaplin, W. J.; Verner,
G. A.; Bedding, T. R.; Catala, C.; Gazzano, J. -C.; Molenda-Żakowicz,
J.; Thygesen, A. O.; Uytterhoeven, K.; Hekker, S.; Huber, D.; Karoff,
C.; Mathur, S.; Mosser, B.; Appourchaux, T.; Campante, T. L.; Elsworth,
Y.; García, R. A.; Handberg, R.; Metcalfe, T. S.; Quirion, P. -O.;
Régulo, C.; Roxburgh, I. W.; Stello, D.; Christensen-Dalsgaard,
J.; Kawaler, S. D.; Kjeldsen, H.; Morris, R. L.; Quintana, E. V.;
Sanderfer, D. T.
2012MNRAS.423..122B Altcode: 2012arXiv1203.0611B; 2012MNRAS.tmp.3037B
We present a detailed spectroscopic study of 93 solar-type stars
that are targets of the NASA/Kepler mission and provide detailed
chemical composition of each target. We find that the overall
metallicity is well represented by Fe lines. Relative abundances
of light elements (CNO) and α elements are generally higher for
low-metallicity stars. Our spectroscopic analysis benefits from the
accurately measured surface gravity from the asteroseismic analysis
of the Kepler light curves. The accuracy on the log g parameter is
better than 0.03 dex and is held fixed in the analysis. We compare
our T<SUB>eff</SUB> determination with a recent colour calibration of
V<SUB>T</SUB>-K<SUB>S</SUB> [TYCHO V magnitude minus Two Micron All Sky
Survey (2MASS) K<SUB>S</SUB> magnitude] and find very good agreement
and a scatter of only 80 K, showing that for other nearby Kepler
targets, this index can be used. The asteroseismic log g values agree
very well with the classical determination using Fe I-Fe II balance,
although we find a small systematic offset of 0.08 dex (asteroseismic
log g values are lower). The abundance patterns of metals, α elements
and the light elements (CNO) show that a simple scaling by [Fe/H]
is adequate to represent the metallicity of the stars, except for
the stars with metallicity below -0.3, where α-enhancement becomes
important. However, this is only important for a very small fraction of
the Kepler sample. We therefore recommend that a simple scaling with
[Fe/H] be employed in the asteroseismic analyses of large ensembles
of solar-type stars.
---------------------------------------------------------
Title: Solving the Mode Identification Problem in Asteroseismology
of F Stars Observed with Kepler
Authors: White, Timothy R.; Bedding, Timothy R.; Gruberbauer, Michael;
Benomar, Othman; Stello, Dennis; Appourchaux, Thierry; Chaplin,
William J.; Christensen-Dalsgaard, Jørgen; Elsworth, Yvonne P.;
García, Rafael A.; Hekker, Saskia; Huber, Daniel; Kjeldsen, Hans;
Mosser, Benoît; Kinemuchi, Karen; Mullally, Fergal; Still, Martin
2012ApJ...751L..36W Altcode: 2012arXiv1205.0544W
Asteroseismology of F-type stars has been hindered by an ambiguity in
identification of their oscillation modes. The regular mode pattern
that makes this task trivial in cooler stars is masked by increased
line widths. The absolute mode frequencies, encapsulated in the
asteroseismic variable epsilon, can help solve this impasse because
the values of epsilon implied by the two possible mode identifications
are distinct. We find that the correct epsilon can be deduced from the
effective temperature and the line widths and we apply these methods
to a sample of solar-like oscillators observed with Kepler.
---------------------------------------------------------
Title: Damping rates of solar-like oscillations across the HR
diagram. Theoretical calculations confronted to CoRoT and Kepler
observations
Authors: Belkacem, K.; Dupret, M. A.; Baudin, F.; Appourchaux, T.;
Marques, J. P.; Samadi, R.
2012A&A...540L...7B Altcode: 2012arXiv1203.1737B
The space-borne missions CoRoT and Kepler are providing a rich harvest
of high-quality constraints on solar-like pulsators. Among the seismic
parameters, mode damping rates remains poorly understood and are thus
barely used to infer the physical properties of stars. Nevertheless,
thanks to the CoRoT and Kepler spacecrafts it is now possible to measure
damping rates for hundreds of main-sequence and thousands of red-giant
stars with unprecedented precision. By using a non-adiabatic pulsation
code including a time-dependent convection treatment, we compute
damping rates for stellar models that are representative of solar-like
pulsators from the main-sequence to the red-giant phase. This allows us
to reproduce the observations of both CoRoT and Kepler, which validates
our modeling of mode damping rates and thus the underlying physical
mechanisms included in the modeling. By considering the perturbations
of turbulent pressure and entropy (including the perturbation of the
dissipation rate of turbulent energy into heat) by the oscillation
in our computation, we succeed in reproducing the observed relation
between damping rates and effective temperature. Moreover, we discuss
the physical reasons for mode damping rates to scale with effective
temperature, as observationally exhibited. Finally, this opens the
way for the use of mode damping rates to probe turbulent convection
in solar-like stars.
---------------------------------------------------------
Title: A Uniform Asteroseismic Analysis of 22 Solar-type Stars
Observed by Kepler
Authors: Mathur, S.; Metcalfe, T. S.; Woitaszek, M.; Bruntt, H.;
Verner, G. A.; Christensen-Dalsgaard, J.; Creevey, O. L.; Doǧan, G.;
Basu, S.; Karoff, C.; Stello, D.; Appourchaux, T.; Campante, T. L.;
Chaplin, W. J.; García, R. A.; Bedding, T. R.; Benomar, O.; Bonanno,
A.; Deheuvels, S.; Elsworth, Y.; Gaulme, P.; Guzik, J. A.; Handberg,
R.; Hekker, S.; Herzberg, W.; Monteiro, M. J. P. F. G.; Piau, L.;
Quirion, P. -O.; Régulo, C.; Roth, M.; Salabert, D.; Serenelli, A.;
Thompson, M. J.; Trampedach, R.; White, T. R.; Ballot, J.; Brandão,
I. M.; Molenda-Żakowicz, J.; Kjeldsen, H.; Twicken, J. D.; Uddin,
K.; Wohler, B.
2012ApJ...749..152M Altcode: 2012arXiv1202.2844M
Asteroseismology with the Kepler space telescope is providing not
only an improved characterization of exoplanets and their host stars,
but also a new window on stellar structure and evolution for the
large sample of solar-type stars in the field. We perform a uniform
analysis of 22 of the brightest asteroseismic targets with the highest
signal-to-noise ratio observed for 1 month each during the first year
of the mission, and we quantify the precision and relative accuracy
of asteroseismic determinations of the stellar radius, mass, and age
that are possible using various methods. We present the properties
of each star in the sample derived from an automated analysis of the
individual oscillation frequencies and other observational constraints
using the Asteroseismic Modeling Portal (AMP), and we compare them to
the results of model-grid-based methods that fit the global oscillation
properties. We find that fitting the individual frequencies typically
yields asteroseismic radii and masses to ~1% precision, and ages to
~2.5% precision (respectively, 2, 5, and 8 times better than fitting
the global oscillation properties). The absolute level of agreement
between the results from different approaches is also encouraging,
with model-grid-based methods yielding slightly smaller estimates of
the radius and mass and slightly older values for the stellar age
relative to AMP, which computes a large number of dedicated models
for each star. The sample of targets for which this type of analysis
is possible will grow as longer data sets are obtained during the
remainder of the mission.
---------------------------------------------------------
Title: Asteroseismology of the Solar Analogs 16 Cyg A and B from
Kepler Observations
Authors: Metcalfe, T. S.; Chaplin, W. J.; Appourchaux, T.; García,
R. A.; Basu, S.; Brandão, I.; Creevey, O. L.; Deheuvels, S.; Doǧan,
G.; Eggenberger, P.; Karoff, C.; Miglio, A.; Stello, D.; Yıldız,
M.; Çelik, Z.; Antia, H. M.; Benomar, O.; Howe, R.; Régulo, C.;
Salabert, D.; Stahn, T.; Bedding, T. R.; Davies, G. R.; Elsworth, Y.;
Gizon, L.; Hekker, S.; Mathur, S.; Mosser, B.; Bryson, S. T.; Still,
M. D.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.;
Kjeldsen, H.; Ibrahim, K. A.; Klaus, T. C.; Li, J.
2012ApJ...748L..10M Altcode: 2012arXiv1201.5966M
The evolved solar-type stars 16 Cyg A and B have long been studied
as solar analogs, yielding a glimpse into the future of our own
Sun. The orbital period of the binary system is too long to provide
meaningful dynamical constraints on the stellar properties, but
asteroseismology can help because the stars are among the brightest
in the Kepler field. We present an analysis of three months of nearly
uninterrupted photometry of 16 Cyg A and B from the Kepler space
telescope. We extract a total of 46 and 41 oscillation frequencies
for the two components, respectively, including a clear detection
of octupole (l = 3) modes in both stars. We derive the properties
of each star independently using the Asteroseismic Modeling Portal,
fitting the individual oscillation frequencies and other observational
constraints simultaneously. We evaluate the systematic uncertainties
from an ensemble of results generated by a variety of stellar evolution
codes and fitting methods. The optimal models derived by fitting each
component individually yield a common age (t = 6.8 ± 0.4 Gyr) and
initial composition (Z <SUB>i</SUB> = 0.024 ± 0.002, Y <SUB>i</SUB> =
0.25 ± 0.01) within the uncertainties, as expected for the components
of a binary system, bolstering our confidence in the reliability of
asteroseismic techniques. The longer data sets that will ultimately
become available will allow future studies of differential rotation,
convection zone depths, and long-term changes due to stellar activity
cycles.
---------------------------------------------------------
Title: Acoustic spectrum fitting for a large set of solar-like
pulsators
Authors: Benomar, O.; Baudin, F.; Chaplin, W. J.; Elsworth, Y.;
Appourchaux, T.
2012MNRAS.420.2178B Altcode: 2011MNRAS.tmp.2149B
Asteroseismology provides the means both to constrain the global
properties and to probe the internal structures of stars. Asteroseismic
data are now available on large numbers of solar-type stars, thanks
in particular to the CoRoT and Kepler space missions, and automated
data-analysis pipelines are needed to provide efficient and timely
results. Here, we present an automated algorithm that is able to extract
mode parameters under low signal-to-noise ratio conditions. We use a
Bayesian framework to ensure the robustness of the algorithm. We discuss
the efficiency of the method and test it using Variability of Solar
Irradiance and Gravity Oscillations (VIRGO) Sun-as-a-star photometry
data and the artificial Astero Fitting at Low Angular degree Group
(asteroFLAG) Kepler ensemble. Analysis of the VIRGO data shows that
it is possible to track variations of the individual mode parameters
(frequency, height, width) through the solar cycle, using short time
series (30 days). The present analysis also revealed a modulation
of the degree l = 2 relative height through the solar cycle. Applied
on asteroFLAG data, we show that the pipeline extracts accurately the
central frequency and the large separation. It is also able to identify
the degree of the modes in 78 per cent of stars.
---------------------------------------------------------
Title: Kepler-21b: A 1.6 R <SUB>Earth</SUB> Planet Transiting the
Bright Oscillating F Subgiant Star HD 179070
Authors: Howell, Steve B.; Rowe, Jason F.; Bryson, Stephen T.; Quinn,
Samuel N.; Marcy, Geoffrey W.; Isaacson, Howard; Ciardi, David R.;
Chaplin, William J.; Metcalfe, Travis S.; Monteiro, Mario J. P. F. G.;
Appourchaux, Thierry; Basu, Sarbani; Creevey, Orlagh L.; Gilliland,
Ronald L.; Quirion, Pierre-Olivier; Stello, Denis; Kjeldsen, Hans;
Christensen-Dalsgaard, Jörgen; Elsworth, Yvonne; García, Rafael
A.; Houdek, Günter; Karoff, Christoffer; Molenda-Żakowicz, Joanna;
Thompson, Michael J.; Verner, Graham A.; Torres, Guillermo; Fressin,
Francois; Crepp, Justin R.; Adams, Elisabeth; Dupree, Andrea; Sasselov,
Dimitar D.; Dressing, Courtney D.; Borucki, William J.; Koch, David
G.; Lissauer, Jack J.; Latham, David W.; Buchhave, Lars A.; Gautier,
Thomas N., III; Everett, Mark; Horch, Elliott; Batalha, Natalie M.;
Dunham, Edward W.; Szkody, Paula; Silva, David R.; Mighell, Ken;
Holberg, Jay; Ballot, Jerôme; Bedding, Timothy R.; Bruntt, Hans;
Campante, Tiago L.; Handberg, Rasmus; Hekker, Saskia; Huber, Daniel;
Mathur, Savita; Mosser, Benoit; Régulo, Clara; White, Timothy R.;
Christiansen, Jessie L.; Middour, Christopher K.; Haas, Michael R.;
Hall, Jennifer R.; Jenkins, Jon M.; McCaulif, Sean; Fanelli, Michael
N.; Kulesa, Craig; McCarthy, Don; Henze, Christopher E.
2012ApJ...746..123H Altcode: 2011arXiv1112.2165H
We present Kepler observations of the bright (V = 8.3), oscillating
star HD 179070. The observations show transit-like events which
reveal that the star is orbited every 2.8 days by a small, 1.6 R
<SUB>Earth</SUB> object. Seismic studies of HD 179070 using short
cadence Kepler observations show that HD 179070 has a frequency-power
spectrum consistent with solar-like oscillations that are acoustic
p-modes. Asteroseismic analysis provides robust values for the mass
and radius of HD 179070, 1.34 ± 0.06 M <SUB>⊙</SUB> and 1.86 ±
0.04 R <SUB>⊙</SUB>, respectively, as well as yielding an age of
2.84 ± 0.34 Gyr for this F5 subgiant. Together with ground-based
follow-up observations, analysis of the Kepler light curves and
image data, and blend scenario models, we conservatively show at the
>99.7% confidence level (3σ) that the transit event is caused by
a 1.64 ± 0.04 R <SUB>Earth</SUB> exoplanet in a 2.785755 ± 0.000032
day orbit. The exoplanet is only 0.04 AU away from the star and our
spectroscopic observations provide an upper limit to its mass of ~10 M
<SUB>Earth</SUB> (2σ). HD 179070 is the brightest exoplanet host star
yet discovered by Kepler. <P />Based in part on observations obtained
at the W. M. Keck Observatory, which is operated by the University
of California and the California Institute of Technology, the Mayall
telescope at Kitt Peak National Observatory, and the WIYN Observatory
which is a joint facility of NOAO, University of Wisconsin-Madison,
Indiana University, and Yale University.
---------------------------------------------------------
Title: Oscillation mode linewidths of main-sequence and subgiant
stars observed by Kepler
Authors: Appourchaux, T.; Benomar, O.; Gruberbauer, M.; Chaplin,
W. J.; García, R. A.; Handberg, R.; Verner, G. A.; Antia, H. M.;
Campante, T. L.; Davies, G. R.; Deheuvels, S.; Hekker, S.; Howe,
R.; Salabert, D.; Bedding, T. R.; White, T. R.; Houdek, G.; Silva
Aguirre, V.; Elsworth, Y. P.; van Cleve, J.; Clarke, B. D.; Hall,
J. R.; Kjeldsen, H.
2012A&A...537A.134A Altcode: 2011arXiv1112.3295A
Context. Solar-like oscillations have been observed by Kepler and CoRoT
in several solar-type stars. <BR /> Aims: We study the variations in the
stellar p-mode linewidth as a function of effective temperature. <BR
/> Methods: We study a time series of nine months of Kepler data. We
analyse the power spectra of 42 cool main-sequence stars and subgiants
using both maximum likelihood estimators and Bayesian estimators
to recover individual mode characteristics such as frequencies,
linewidths, and mode heights. <BR /> Results: We report on the mode
linewidth at both maximum power and maximum mode height for these 42
stars as a function of effective temperature. <BR /> Conclusions: We
show that the mode linewidth at either maximum mode height or maximum
amplitude follows a scaling relation with effective temperature,
which is a combination of a power law and a lower bound. The typical
power-law index is about 13 for the linewidth derived from the maximum
mode height, and about 16 for the linewidth derived from the maximum
amplitude, while the lower bound is about 0.3 μHz and 0.7 μHz,
respectively. We stress that this scaling relation is only valid for
cool main-sequence stars and subgiants, and does not have any predictive
power outside the temperature range of these stars.
---------------------------------------------------------
Title: Testing Scaling Relations for Solar-like Oscillations from
the Main Sequence to Red Giants Using Kepler Data
Authors: Huber, D.; Bedding, T. R.; Stello, D.; Hekker, S.; Mathur,
S.; Mosser, B.; Verner, G. A.; Bonanno, A.; Buzasi, D. L.; Campante,
T. L.; Elsworth, Y. P.; Hale, S. J.; Kallinger, T.; Silva Aguirre,
V.; Chaplin, W. J.; De Ridder, J.; García, R. A.; Appourchaux,
T.; Frandsen, S.; Houdek, G.; Molenda-Żakowicz, J.; Monteiro,
M. J. P. F. G.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler,
S. D.; Kjeldsen, H.; Broomhall, A. M.; Corsaro, E.; Salabert, D.;
Sanderfer, D. T.; Seader, S. E.; Smith, J. C.
2011ApJ...743..143H Altcode: 2011arXiv1109.3460H
We have analyzed solar-like oscillations in ~1700 stars observed by the
Kepler Mission, spanning from the main sequence to the red clump. Using
evolutionary models, we test asteroseismic scaling relations for the
frequency of maximum power (ν<SUB>max</SUB>), the large frequency
separation (Δν), and oscillation amplitudes. We show that the
difference of the Δν-ν<SUB>max</SUB> relation for unevolved and
evolved stars can be explained by different distributions in effective
temperature and stellar mass, in agreement with what is expected from
scaling relations. For oscillation amplitudes, we show that neither
(L/M)<SUP> s </SUP> scaling nor the revised scaling relation by Kjeldsen
& Bedding is accurate for red-giant stars, and demonstrate that a
revised scaling relation with a separate luminosity-mass dependence can
be used to calculate amplitudes from the main sequence to red giants
to a precision of ~25%. The residuals show an offset particularly for
unevolved stars, suggesting that an additional physical dependency is
necessary to fully reproduce the observed amplitudes. We investigate
correlations between amplitudes and stellar activity, and find evidence
that the effect of amplitude suppression is most pronounced for subgiant
stars. Finally, we test the location of the cool edge of the instability
strip in the Hertzsprung-Russell diagram using solar-like oscillations
and find the detections in the hottest stars compatible with a domain
of hybrid stochastically excited and opacity driven pulsation.
---------------------------------------------------------
Title: Asteroseismic Diagrams from a Survey of Solar-like Oscillations
with Kepler
Authors: White, Timothy R.; Bedding, Timothy R.; Stello, Dennis;
Appourchaux, Thierry; Ballot, Jérôme; Benomar, Othman; Bonanno,
Alfio; Broomhall, Anne-Marie; Campante, Tiago L.; Chaplin, William
J.; Christensen-Dalsgaard, Jørgen; Corsaro, Enrico; Doǧan, Gülnur;
Elsworth, Yvonne P.; Fletcher, Stephen T.; García, Rafael A.; Gaulme,
Patrick; Handberg, Rasmus; Hekker, Saskia; Huber, Daniel; Karoff,
Christoffer; Kjeldsen, Hans; Mathur, Savita; Mosser, Benoit; Monteiro,
Mario J. P. F. G.; Régulo, Clara; Salabert, David; Silva Aguirre,
Victor; Thompson, Michael J.; Verner, Graham; Morris, Robert L.;
Sanderfer, Dwight T.; Seader, Shawn E.
2011ApJ...742L...3W Altcode: 2011arXiv1110.1375W
Photometric observations made by the NASA Kepler Mission have led to a
dramatic increase in the number of main-sequence and subgiant stars with
detected solar-like oscillations. We present an ensemble asteroseismic
analysis of 76 solar-type stars. Using frequencies determined from the
Kepler time-series photometry, we have measured three asteroseismic
parameters that characterize the oscillations: the large frequency
separation (Δν), the small frequency separation between modes of
l = 0 and l = 2 (δν<SUB>02</SUB>), and the dimensionless offset
(epsilon). These measurements allow us to construct asteroseismic
diagrams, namely the so-called Christensen-Dalsgaard diagram of
δν<SUB>02</SUB> versus Δν, and the recently re-introduced epsilon
diagram. We compare the Kepler results with previously observed
solar-type stars and with theoretical models. The positions of
stars in these diagrams places constraints on their masses and
ages. Additionally, we confirm the observational relationship
between epsilon and T <SUB>eff</SUB> that allows for the unambiguous
determination of radial order and should help resolve the problem of
mode identification in F stars.
---------------------------------------------------------
Title: Constructing a One-solar-mass Evolutionary Sequence Using
Asteroseismic Data from Kepler
Authors: Silva Aguirre, V.; Chaplin, W. J.; Ballot, J.; Basu,
S.; Bedding, T. R.; Serenelli, A. M.; Verner, G. A.; Miglio, A.;
Monteiro, M. J. P. F. G.; Weiss, A.; Appourchaux, T.; Bonanno,
A.; Broomhall, A. M.; Bruntt, H.; Campante, T. L.; Casagrande, L.;
Corsaro, E.; Elsworth, Y.; García, R. A.; Gaulme, P.; Handberg,
R.; Hekker, S.; Huber, D.; Karoff, C.; Mathur, S.; Mosser, B.;
Salabert, D.; Schönrich, R.; Sousa, S. G.; Stello, D.; White, T. R.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.; Kjeldsen,
H.; Houdek, G.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Thompson,
M. J.; Caldwell, D. A.; Christiansen, J. L.; Wohler, B.
2011ApJ...740L...2S Altcode: 2011arXiv1108.2031S
Asteroseismology of solar-type stars has entered a new era of
large surveys with the success of the NASA Kepler mission, which
is providing exquisite data on oscillations of stars across the
Hertzsprung-Russell diagram. From the time-series photometry, the two
seismic parameters that can be most readily extracted are the large
frequency separation (Δν) and the frequency of maximum oscillation
power (ν<SUB>max</SUB>). After the survey phase, these quantities
are available for hundreds of solar-type stars. By scaling from solar
values, we use these two asteroseismic observables to identify for the
first time an evolutionary sequence of 1 M <SUB>sun</SUB> field stars,
without the need for further information from stellar models. Comparison
of our determinations with the few available spectroscopic results
shows an excellent level of agreement. We discuss the potential of the
method for differential analysis throughout the main-sequence evolution
and the possibility of detecting twins of very well-known stars.
---------------------------------------------------------
Title: Asteroseismology from multi-month Kepler photometry: the
evolved Sun-like stars KIC 10273246 and KIC 10920273
Authors: Campante, T. L.; Handberg, R.; Mathur, S.; Appourchaux, T.;
Bedding, T. R.; Chaplin, W. J.; García, R. A.; Mosser, B.; Benomar,
O.; Bonanno, A.; Corsaro, E.; Fletcher, S. T.; Gaulme, P.; Hekker, S.;
Karoff, C.; Régulo, C.; Salabert, D.; Verner, G. A.; White, T. R.;
Houdek, G.; Brandão, I. M.; Creevey, O. L.; Doǧan, G.; Bazot,
M.; Christensen-Dalsgaard, J.; Cunha, M. S.; Elsworth, Y.; Huber,
D.; Kjeldsen, H.; Lundkvist, M.; Molenda-Żakowicz, J.; Monteiro,
M. J. P. F. G.; Stello, D.; Clarke, B. D.; Girouard, F. R.; Hall, J. R.
2011A&A...534A...6C Altcode: 2011arXiv1108.3807C
Context. The evolved main-sequence Sun-like stars KIC 10273246 (F-type)
and KIC 10920273 (G-type) were observed with the NASA Kepler satellite
for approximately ten months with a duty cycle in excess of 90%. Such
continuous and long observations are unprecedented for solar-type
stars other than the Sun. <BR /> Aims: We aimed mainly at extracting
estimates of p-mode frequencies - as well as of other individual mode
parameters - from the power spectra of the light curves of both stars,
thus providing scope for a full seismic characterization. <BR />
Methods: The light curves were corrected for instrumental effects in
a manner independent of the Kepler science pipeline. Estimation of
individual mode parameters was based both on the maximization of the
likelihood of a model describing the power spectrum and on a classic
prewhitening method. Finally, we employed a procedure for selecting
frequency lists to be used in stellar modeling. <BR /> Results: A
total of 30 and 21 modes of degree l = 0,1,2 - spanning at least eight
radial orders - have been identified for KIC 10273246 and KIC 10920273,
respectively. Two avoided crossings (l = 1 ridge) have been identified
for KIC 10273246, whereas one avoided crossing plus another likely
one have been identified for KIC 10920273. Good agreement is found
between observed and predicted mode amplitudes for the F-type star KIC
10273246, based on a revised scaling relation. Estimates are given of
the rotational periods, the parameters describing stellar granulation
and the global asteroseismic parameters Δν and ν<SUB>max</SUB>.
---------------------------------------------------------
Title: Verification of the Kepler Input Catalog from Asteroseismology
of Solar-type Stars
Authors: Verner, G. A.; Chaplin, W. J.; Basu, S.; Brown, T. M.;
Hekker, S.; Huber, D.; Karoff, C.; Mathur, S.; Metcalfe, T. S.;
Mosser, B.; Quirion, P. -O.; Appourchaux, T.; Bedding, T. R.; Bruntt,
H.; Campante, T. L.; Elsworth, Y.; García, R. A.; Handberg, R.;
Régulo, C.; Roxburgh, I. W.; Stello, D.; Christensen-Dalsgaard, J.;
Gilliland, R. L.; Kawaler, S. D.; Kjeldsen, H.; Allen, C.; Clarke,
B. D.; Girouard, F. R.
2011ApJ...738L..28V Altcode: 2011arXiv1109.0869V
We calculate precise stellar radii and surface gravities from the
asteroseismic analysis of over 500 solar-type pulsating stars observed
by the Kepler space telescope. These physical stellar properties
are compared with those given in the Kepler Input Catalog (KIC),
determined from ground-based multi-color photometry. For the stars
in our sample, we find general agreement but we detect an average
overestimation bias of 0.23 dex in the KIC determination of log (g)
for stars with log (g)<SUB>KIC</SUB> > 4.0 dex, and a resultant
underestimation bias of up to 50% in the KIC radii estimates for stars
with R <SUB>KIC</SUB> < 2 R <SUB>sun</SUB>. Part of the difference
may arise from selection bias in the asteroseismic sample; nevertheless,
this result implies there may be fewer stars characterized in the KIC
with R ~ 1 R <SUB>sun</SUB> than is suggested by the physical properties
in the KIC. Furthermore, if the radius estimates are taken from the
KIC for these affected stars and then used to calculate the size of
transiting planets, a similar underestimation bias may be applied to
the planetary radii.
---------------------------------------------------------
Title: Global asteroseismic properties of solar-like oscillations
observed by Kepler: a comparison of complementary analysis methods
Authors: Verner, G. A.; Elsworth, Y.; Chaplin, W. J.; Campante,
T. L.; Corsaro, E.; Gaulme, P.; Hekker, S.; Huber, D.; Karoff, C.;
Mathur, S.; Mosser, B.; Appourchaux, T.; Ballot, J.; Bedding, T. R.;
Bonanno, A.; Broomhall, A. -M.; García, R. A.; Handberg, R.; New,
R.; Stello, D.; Régulo, C.; Roxburgh, I. W.; Salabert, D.; White,
T. R.; Caldwell, D. A.; Christiansen, J. L.; Fanelli, M. N.
2011MNRAS.415.3539V Altcode: 2011MNRAS.tmp..892V; 2011arXiv1105.0571V
We present the asteroseismic analysis of 1948 F-, G- and K-type
main-sequence and subgiant stars observed by the National Aeronautics
and Space Administration Kepler mission. We detect and characterize
solar-like oscillations in 642 of these stars. This represents the
largest cohort of main-sequence and subgiant solar-like oscillators
observed to date. The photometric observations are analysed using the
methods developed by nine independent research teams. The results are
combined to validate the determined global asteroseismic parameters
and calculate the relative precision by which the parameters can be
obtained. We correlate the relative number of detected solar-like
oscillators with stellar parameters from the Kepler Input Catalogue
and find a deficiency for stars with effective temperatures in the
range 5300 ≲T<SUB>eff</SUB>≲ 5700 K and a drop-off in detected
oscillations in stars approaching the red edge of the classical
instability strip. We compare the power-law relationships between the
frequency of peak power, ν<SUB>max</SUB>, the mean large frequency
separation, Δν, and the maximum mode amplitude, A<SUB>max</SUB>,
and show that there are significant method-dependent differences in the
results obtained. This illustrates the need for multiple complementary
analysis methods to be used to assess the robustness and reproducibility
of results derived from global asteroseismic parameters.
---------------------------------------------------------
Title: Solar-like Oscillations in KIC 11395018 and KIC 11234888 from
8 Months of Kepler Data
Authors: Mathur, S.; Handberg, R.; Campante, T. L.; García, R. A.;
Appourchaux, T.; Bedding, T. R.; Mosser, B.; Chaplin, W. J.; Ballot,
J.; Benomar, O.; Bonanno, A.; Corsaro, E.; Gaulme, P.; Hekker,
S.; Régulo, C.; Salabert, D.; Verner, G.; White, T. R.; Brandão,
I. M.; Creevey, O. L.; Doǧan, G.; Elsworth, Y.; Huber, D.; Hale,
S. J.; Houdek, G.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz,
J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Christensen-Dalsgaard,
J.; Gilliland, R. L.; Kawaler, S. D.; Kjeldsen, H.; Quintana, E. V.;
Sanderfer, D. T.; Seader, S. E.
2011ApJ...733...95M Altcode: 2011arXiv1103.4085M
We analyze the photometric short-cadence data obtained with the Kepler
mission during the first 8 months of observations of two solar-type
stars of spectral types G and F: KIC 11395018 and KIC 11234888,
respectively, the latter having a lower signal-to-noise ratio (S/N)
compared with the former. We estimate global parameters of the acoustic
(p) modes such as the average large and small frequency separations, the
frequency of the maximum of the p-mode envelope, and the average line
width of the acoustic modes. We were able to identify and to measure
22 p-mode frequencies for the first star and 16 for the second one
even though the S/N of these stars are rather low. We also derive some
information about the stellar rotation periods from the analyses of the
low-frequency parts of the power spectral densities. A model-independent
estimation of the mean density, mass, and radius is obtained using the
scaling laws. We emphasize the importance of continued observations
for the stars with low S/N for an improved characterization of the
oscillation modes. Our results offer a preview of what will be possible
for many stars with the long data sets obtained during the remainder
of the mission.
---------------------------------------------------------
Title: Preparation of Kepler light curves for asteroseismic analyses
Authors: García, R. A.; Hekker, S.; Stello, D.; Gutiérrez-Soto,
J.; Handberg, R.; Huber, D.; Karoff, C.; Uytterhoeven, K.;
Appourchaux, T.; Chaplin, W. J.; Elsworth, Y.; Mathur, S.; Ballot,
J.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Houdek, G.; Jenkins,
J. M.; Kjeldsen, H.; McCauliff, S.; Metcalfe, T.; Middour, C. K.;
Molenda-Zakowicz, J.; Monteiro, M. J. P. F. G.; Smith, J. C.; Thompson,
M. J.
2011MNRAS.414L...6G Altcode: 2011arXiv1103.0382G
The Kepler mission is providing photometric data of exquisite
quality for the asteroseismic study of different classes of pulsating
stars. These analyses place particular demands on the pre-processing
of the data, over a range of time-scales from minutes to months. Here,
we describe processing procedures developed by the Kepler Asteroseismic
Science Consortium to prepare light curves that are optimized for the
asteroseismic study of solar-like oscillating stars in which outliers,
jumps and drifts are corrected.
---------------------------------------------------------
Title: Accurate p-mode measurements of the G0V metal-rich CoRoT
target HD 52265
Authors: Ballot, J.; Gizon, L.; Samadi, R.; Vauclair, G.; Benomar, O.;
Bruntt, H.; Mosser, B.; Stahn, T.; Verner, G. A.; Campante, T. L.;
García, R. A.; Mathur, S.; Salabert, D.; Gaulme, P.; Régulo, C.;
Roxburgh, I. W.; Appourchaux, T.; Baudin, F.; Catala, C.; Chaplin,
W. J.; Deheuvels, S.; Michel, E.; Bazot, M.; Creevey, O.; Dolez, N.;
Elsworth, Y.; Sato, K. H.; Vauclair, S.; Auvergne, M.; Baglin, A.
2011A&A...530A..97B Altcode: 2011arXiv1105.3551B
Context. The star <ASTROBJ>HD 52265</ASTROBJ> is a G0V metal-rich
exoplanet-host star observed in the seismology field of the CoRoT
space telescope from November 2008 to March 2009. The satellite
collected 117 days of high-precision photometric data on this star,
showing that it presents solar-like oscillations. HD 52265 was also
observed in spectroscopy with the Narval spectrograph at the same
epoch. <BR /> Aims: We characterise HD 52265 using both spectroscopic
and seismic data. <BR /> Methods: The fundamental stellar parameters
of HD 52265 were derived with the semi-automatic software VWA, and
the projected rotational velocity was estimated by fitting synthetic
profiles to isolated lines in the observed spectrum. The parameters
of the observed p modes were determined with a maximum-likelihood
estimation. We performed a global fit of the oscillation spectrum,
over about ten radial orders, for degrees l = 0 to 2. We also derived
the properties of the granulation, and analysed a signature of the
rotation induced by the photospheric magnetic activity. <BR /> Results:
Precise determinations of fundamental parameters have been obtained:
T<SUB>eff</SUB> = 6100 ± 60 K, log g = 4.35 ± 0.09, [M/H] = 0.19 ±
0.05, as well as vsini=3.6<SUP>+0.3</SUP><SUB>-1.0kms</SUB>. We have
measured a mean rotation period P<SUB>rot</SUB> = 12.3 ± 0.15 days,
and find a signature of differential rotation. The frequencies of 31
modes are reported in the range 1500-2550 μHz. The large separation
exhibits a clear modulation around the mean value Dnu=98.3 ± 0.1
μHz. Mode widths vary with frequency along an S-shape with a clear
local maximum around 1800 μHz. We deduce lifetimes ranging between
0.5 and 3 days for these modes. Finally, we find a maximal bolometric
amplitude of about 3.96 ± 0.24 ppm for radial modes. <P />The CoRoT
space mission, launched on December 27th 2006, has been developed
and is operated by CNES, with the contribution of Austria, Belgium,
Brazil, ESA (RSSD and Science Programme), Germany and Spain.
---------------------------------------------------------
Title: Predicting the Detectability of Oscillations in Solar-type
Stars Observed by Kepler
Authors: Chaplin, W. J.; Kjeldsen, H.; Bedding, T. R.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.;
Appourchaux, T.; Elsworth, Y.; García, R. A.; Houdek, G.; Karoff, C.;
Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.;
Thompson, M. J.; Verner, G. A.; Batalha, N.; Borucki, W. J.;
Brown, T. M.; Bryson, S. T.; Christiansen, J. L.; Clarke, B. D.;
Jenkins, J. M.; Klaus, T. C.; Koch, D.; An, D.; Ballot, J.; Basu,
S.; Benomar, O.; Bonanno, A.; Broomhall, A. -M.; Campante, T. L.;
Corsaro, E.; Creevey, O. L.; Esch, L.; Gai, N.; Gaulme, P.; Hale,
S. J.; Handberg, R.; Hekker, S.; Huber, D.; Mathur, S.; Mosser, B.;
New, R.; Pinsonneault, M. H.; Pricopi, D.; Quirion, P. -O.; Régulo,
C.; Roxburgh, I. W.; Salabert, D.; Stello, D.; Suran, M. D.
2011ApJ...732...54C Altcode: 2011arXiv1103.0702C
Asteroseismology of solar-type stars has an important part to play
in the exoplanet program of the NASA Kepler Mission. Precise and
accurate inferences on the stellar properties that are made possible
by the seismic data allow very tight constraints to be placed on the
exoplanetary systems. Here, we outline how to make an estimate of the
detectability of solar-like oscillations in any given Kepler target,
using rough estimates of the temperature and radius, and the Kepler
apparent magnitude.
---------------------------------------------------------
Title: Evidence for the Impact of Stellar Activity on the
Detectability of Solar-like Oscillations Observed by Kepler
Authors: Chaplin, W. J.; Bedding, T. R.; Bonanno, A.; Broomhall,
A. -M.; García, R. A.; Hekker, S.; Huber, D.; Verner, G. A.;
Basu, S.; Elsworth, Y.; Houdek, G.; Mathur, S.; Mosser, B.; New,
R.; Stevens, I. R.; Appourchaux, T.; Karoff, C.; Metcalfe, T. S.;
Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.; Thompson, M. J.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Kawaler, S. D.; Kjeldsen,
H.; Ballot, J.; Benomar, O.; Corsaro, E.; Campante, T. L.; Gaulme,
P.; Hale, S. J.; Handberg, R.; Jarvis, E.; Régulo, C.; Roxburgh,
I. W.; Salabert, D.; Stello, D.; Mullally, F.; Li, J.; Wohler, W.
2011ApJ...732L...5C Altcode: 2011arXiv1103.5570C
We use photometric observations of solar-type stars, made by the NASA
Kepler Mission, to conduct a statistical study of the impact of stellar
surface activity on the detectability of solar-like oscillations. We
find that the number of stars with detected oscillations falls
significantly with increasing levels of activity. The results present
strong evidence for the impact of magnetic activity on the properties
of near-surface convection in the stars, which appears to inhibit
the amplitudes of the stochastically excited, intrinsically damped
solar-like oscillations.
---------------------------------------------------------
Title: Ensemble Asteroseismology of Solar-Type Stars with the NASA
Kepler Mission
Authors: Chaplin, W. J.; Kjeldsen, H.; Christensen-Dalsgaard, J.;
Basu, S.; Miglio, A.; Appourchaux, T.; Bedding, T. R.; Elsworth, Y.;
García, R. A.; Gilliland, R. L.; Girardi, L.; Houdek, G.; Karoff,
C.; Kawaler, S. D.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro,
M. J. P. F. G.; Thompson, M. J.; Verner, G. A.; Ballot, J.; Bonanno,
A.; Brandão, I. M.; Broomhall, A. -M.; Bruntt, H.; Campante, T. L.;
Corsaro, E.; Creevey, O. L.; Doğan, G.; Esch, L.; Gai, N.; Gaulme,
P.; Hale, S. J.; Handberg, R.; Hekker, S.; Huber, D.; Jiménez, A.;
Mathur, S.; Mazumdar, A.; Mosser, B.; New, R.; Pinsonneault, M. H.;
Pricopi, D.; Quirion, P. -O.; Régulo, C.; Salabert, D.; Serenelli,
A. M.; Silva Aguirre, V.; Sousa, S. G.; Stello, D.; Stevens, I. R.;
Suran, M. D.; Uytterhoeven, K.; White, T. R.; Borucki, W. J.; Brown,
T. M.; Jenkins, J. M.; Kinemuchi, K.; Van Cleve, J.; Klaus, T. C.
2011Sci...332..213C Altcode: 2011arXiv1109.4723C
In addition to its search for extrasolar planets, the NASA Kepler
mission provides exquisite data on stellar oscillations. We report the
detections of oscillations in 500 solar-type stars in the Kepler field
of view, an ensemble that is large enough to allow statistical studies
of intrinsic stellar properties (such as mass, radius, and age) and
to test theories of stellar evolution. We find that the distribution
of observed masses of these stars shows intriguing differences to
predictions from models of synthetic stellar populations in the Galaxy.
---------------------------------------------------------
Title: The Solar Orbiter Mission and its Polarimetric and Helioseismic
Imager (SO/PHI)
Authors: Gandorfer, Achim; Solanki, Sami K.; Woch, Joachim; Martínez
Pillet, Valentin; Álvarez Herrero, Alberto; Appourchaux, Thierry
2011JPhCS.271a2086G Altcode:
We briefly outline the scientific and instrumental aspects of ESA's
Solar Orbiter mission. Special emphasis is given to the Polarimetric
and Helioseismic Imager, the instrument with the highest relevance for
helioseismology applications, which will observe gas motions and the
vector magnetic field in the photosphere at high spatial and temporal
resolution.
---------------------------------------------------------
Title: PLATO : PLAnetary Transits and Oscillations of stars
Authors: Catala, Claude; Appourchaux, Thierry; Plato Mission Consortium
2011JPhCS.271a2084C Altcode:
PLATO is a M-class candidate in the ESA Cosmic Vision program. PLATO's
objective is to characterize exoplanets and their host stars in
the solar neighbourhood. While it builds on the heritage from CoRoT
and Kepler, the major breakthrough will come from its strong focus
on bright targets (m<SUB>V</SUB> <= 11). The PLATO targets will
also include a large number of very bright (m<SUB>V</SUB> <= 8)
and nearby stars. <P />The prime science goals of PLATO are: (i) the
detection and characterization of exoplanetary systems of all kinds,
including both the planets and their host stars, reaching down to small,
terrestrial planets in the habitable zone; (ii) the identification
of suitable targets for future, more detailed characterization,
including a spectroscopic search for bio-markers in nearby habitable
exoplanets. <P />These ambitious goals will be reached by ultra-high
precision, long (few years), uninterrupted photometric monitoring in
the visible of very large samples of bright stars, which can only be
done from space. The resulting high quality light curves will be used
on the one hand to detect planetary transits, as well as to measure
their characteristics, and on the other hand to provide a seismic
analysis of the host stars of the detected planets, from which precise
measurements of their radii, masses, and ages will be derived. <P
/>The PLATO space-based data will be complemented by ground-based
follow-up observations, in particular very precise radial velocity
monitoring, which will be used to confirm the planetary nature of the
detected events and to measure the planet masses. <P />The full set of
parameters of exoplanetary systems will thus be measured, including
all characteristics of the host stars and the orbits, radii, masses,
and ages of the planets, allowing us to derive planet mean densities,
and estimate their temperature and radiation environment. Finally,
the knowledge of the age of the exoplanetary systems will allow us to
put them in an evolutionary perspective.
---------------------------------------------------------
Title: FOREWORD Foreword
Authors: Appourchaux, Thierry
2011JPhCS.271a1001A Altcode:
Volume 271 (2011) of the Journal of Physics: Conference Series provides
a record of the invited and contributed talks, and of the posters
presented at the GONG2010-SoHO24 conference entitled 'A new era of
seismology of the Sun and solar-like stars'. The conference was held
from 27 June 2010 to 2 July 2010 in Aix-en-Provence, France. More than
120 scientists from all over the world attended the conference. <P
/>I would like to express my gratitude for the the financial support
from the following organisations: Université Paris-Sud; the Centre
National d'Etudes Spatiales (CNES); the Programme National des Relations
Soleil-Terre (PNST) and the Programme National de Physique Stellaire
(PNPS) (both programmes under the umbrella of the Institut National
des Sciences de l'Univers, INSU); INSU of the Centre National de la
Recherche Scientifique (CNRS); the SoHO project of the European Space
Agency (ESA), and the Science Programme of ESA; the Global Oscillations
Network Group (GONG); and finally the European Aeronautic Defence
and Space Company (EADS). <P />The Scientific Organizing Committee
comprised Thierry Appourchaux (chairman, Institut d'Astrophysique
Spatiale, Orsay, France), Frank Hill (co-chairman, GONG / National
Solar Observatory, Tucson, Arizona, United States), Annie Baglin
(Observatoire de Paris-Meudon, France), William Chaplin (University
of Birmingham, United Kingdom), Jørgen Christensen-Dalsgaard (Aarhus
Universitet, Denmark), Thierry Corbard (Observatoire de la Côte d'Azur,
Nice, France), Bernhard Fleck (European Space Agency), Laurent Gizon
(Max-Planck-Institut für Sonnensystemforschung, Lindau, Germany),
Travis Metcalfe (National Center for Atmospheric Research, Boulder,
Colorado, United States), Michael Thompson (Sheffied University, United
Kingdom; High Altitude Observatory, Boulder, Colorado, United States)
and Jesper Schou (Stanford University, California, United States). <P
/>The Editorial Committee of these proceedings was composed of
Thierry Appourchaux (chairman), Annie Baglin, William Chaplin, Jørgen
Christensen-Dalsgaard, Laurent Gizon, Michael Thompson, Takashi Sekii
(National Astronomical Observatory of Japan, Tokyo) and John Leibacher
(IAS, Orsay, France; GONG / NSO, Tucson, Arizona, United States). <P
/>This volume consists of 86 articles organised in sections reflecting
the scientific programme of the conference: <P />012001-012024 Local
helioseismology 012025-012030 Solar diameter, irradiance and activity
012031-012044 Solar and stellar modelling 012045-012056 Low degree
stellar seismology 012057-012063 First results from space missions
012064-012082 Convection, dynamo and flows 012083-012086 Prospective
<P />All papers are freely accessible on the internet, in colour, at <A
href="http://iopscience.iop.org/1742-6596/271/1">http://iopscience.iop.org/1742-6596/271/1</A>,
and an interactive picture of the conference is available in the
attached PDF. <P />I am also grateful to the Local Organizing
Committee for making this conference a success: Catherine Cougrand
(secretary), Stéphane Caminade (web designer), Delphine Prival
(administration) and Jean-Paul Rozet (logistics). I could
not have done it without your help! <P />Last but not least,
let me also thank the official photographer of the conference,
Pierre Assus, for producing excellent photographs, including
the group photo. Please feel free to send me an e-mail at <A
href="Thierry.Appourchaux@ias.u-psud.fr">Thierry.Appourchaux@ias.u-psud.fr</A>
if you would like copies of these pictures. <P />Thierry Appourchaux
Editor <P />Orsay, France 24 December 2010 <P />Conference photograph
<P />IAS logo Université Paris-Sud logo CNRS logo SOHO logo
<P />ESA logo NASA logo Gong logo EADS ASTRIUM logo
---------------------------------------------------------
Title: HD 46375: seismic and spectropolarimetric analysis of a young
Sun hosting a Saturn-like planet
Authors: Gaulme, P.; Deheuvels, S.; Weiss, W. W.; Mosser, B.; Moutou,
C.; Bruntt, H.; Donati, J. -F.; Vannier, M.; Guillot, T.; Appourchaux,
T.; Michel, E.; Auvergne, M.; Samadi, R.; Baudin, F.; Catala, C.;
Baglin, A.
2010A&A...524A..47G Altcode: 2010arXiv1011.2671G
Context. HD 46375 is known to host a Saturn-like exoplanet orbiting at
0.04 AU from its host star. Stellar light reflected by the planet
was tentatively identified in the 34-day CoRoT run acquired in
October-November 2008. <BR /> Aims: We constrain the properties of the
magnetic field of HD 46375 based on spectropolarimetric observations
with the NARVAL spectrograph at the Pic du Midi observatory. In
addition, we use a high-resolution NARVAL flux spectrum to contrain
the atmospheric parameters. With these constraints, we perform
an asteroseismic analysis and modelling of HD 46375 using the
frequencies extracted from the CoRoT light curve. <BR /> Methods:
We used Zeeman Doppler imaging to reconstruct the magnetic map of the
stellar surface. In the spectroscopic analysis we fitted isolated lines
using 1D LTE atmosphere models. This analysis was used to constrain
the effective temperature, surface gravity, and chemical composition
of the star. To extract information about the p-mode oscillations,
we used a technique based on the envelope autocorrelation function
(EACF). <BR /> Results: From the Zeeman Doppler imaging observations,
we observe a magnetic field of ≈ 5 Gauss. From the spectral analysis,
HD 46375 is inferred to be an unevolved K0 type star with high
metallicity [Fe/H] = +0.39. Owing to the relative faintness of the
star (m<SUB>hip</SUB> = 8.05), the signal-to-noise ratio is too low
to identify individual modes. However, we measure the p-mode excess
power and large separation Δν<SUB>0</SUB> = 153.0±0.7 μHz. <BR />
Conclusions: We are able do constrain the fundamental parameters of the
star thanks to spectrometric and seismic analyses. We conclude that
HD 46375 is similar to a young version of α Cen B. This work is of
special interest because of its combination of exoplanetary science
and asteroseismology, which are the subjects of the current Kepler
mission and the proposed Plato mission. <P />The CoRoT space mission,
launched on 2006 December 27, was developed and is operated by the
CNES, with participation of the Science Programs of ESA, ESA's RSSD,
Austria, Belgium, Brazil, Germany and Spain.
---------------------------------------------------------
Title: Asteroseismology of solar-type stars with Kepler I: Data
analysis
Authors: Karoff, C.; Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.;
Garcia, R. A.; Houdek, G.; Metcalfe, T. S.; Molenda-Żakowicz, J.;
Monteiro, M. J. P. F. G.; Thompson, M. J.; Christensen-Dalsgaard, J.;
Gilliland, R. L.; Kjeldsen, H.; Basu, S.; Bedding, T. R.; Campante,
T. L.; Eggenberger, P.; Fletcher, S. T.; Gaulme, P.; Handberg, R.;
Hekker, S.; Martic, M.; Mathur, S.; Mosser, B.; Regulo, C.; Roxburgh,
I. W.; Salabert, D.; Stello, D.; Verner, G. A.; Belkacem, K.; Biazzo,
K.; Cunha, M. S.; Gruberbauer, M.; Guzik, J. A.; Kupka, F.; Leroy,
B.; Ludwig, H. -G.; Mathis, S.; Noels, A.; Noyes, R. W.; Roca Cortes,
T.; Roth, M.; Sato, K. H.; Schmitt, J.; Suran, M. D.; Trampedach,
R.; Uytterhoeven, K.; Ventura, R.
2010AN....331..972K Altcode: 2010arXiv1005.0507K
We report on the first asteroseismic analysis of solar-type stars
observed by Kepler. Observations of three G-type stars, made at
one-minute cadence during the first 33.5 days of science operations,
reveal high signal-to-noise solar-like oscillation spectra in all three
stars: About 20 modes of oscillation can clearly be distinguished
in each star. We discuss the appearance of the oscillation spectra,
including the presence of a possible signature of faculae, and the
presence of mixed modes in one of the three stars.
---------------------------------------------------------
Title: Turbulent eddy-time-correlation in the solar convective zone
Authors: Belkacem, K.; Samadi, R.; Goupil, M. J.; Baudin, F.; Salabert,
D.; Appourchaux, T.
2010A&A...522L...2B Altcode: 2010arXiv1010.2682B
Theoretical modeling of the driving processes of solar-like oscillations
is a powerful way of understanding the properties of the convective
zones of solar-type stars. In this framework, the description of the
temporal correlation between turbulent eddies is an essential ingredient
to model mode amplitudes. However, there is a debate between a Gaussian
or Lorentzian description of the eddy-time correlation function
(Samadi et al. 2003b, A&A, 403, 303; Chaplin et al. 2005, MNRAS,
360, 859). Indeed, a Gaussian description reproduces the low-frequency
shape of the mode amplitude for the Sun, but is unsatisfactory from a
theoretical point of view (Houdek 2010, Ap&SS, 328, 237) and leads
to other disagreements with observations (Samadi et al. 2007, A&A,
463, 297). These are solved by using a Lorentzian description, but
there the low-frequency shape of the solar observations is not correctly
reproduced. We reconcile the two descriptions by adopting the sweeping
approximation, which consists in assuming that the eddy-time-correlation
function is dominated by the advection of eddies, in the inertial range,
by energy-bearing eddies. Using a Lorentzian function together with a
cut-off frequency derived from the sweeping assumption allows us to
reproduce the low-frequency shape of the observations. This result
also constitutes a validation of the sweeping assumption for highly
turbulent flows as in the solar case.
---------------------------------------------------------
Title: A Precise Asteroseismic Age and Radius for the Evolved Sun-like
Star KIC 11026764
Authors: Metcalfe, T. S.; Monteiro, M. J. P. F. G.; Thompson, M. J.;
Molenda-Żakowicz, J.; Appourchaux, T.; Chaplin, W. J.; Doǧan, G.;
Eggenberger, P.; Bedding, T. R.; Bruntt, H.; Creevey, O. L.; Quirion,
P. -O.; Stello, D.; Bonanno, A.; Silva Aguirre, V.; Basu, S.; Esch,
L.; Gai, N.; Di Mauro, M. P.; Kosovichev, A. G.; Kitiashvili, I. N.;
Suárez, J. C.; Moya, A.; Piau, L.; García, R. A.; Marques, J. P.;
Frasca, A.; Biazzo, K.; Sousa, S. G.; Dreizler, S.; Bazot, M.; Karoff,
C.; Frandsen, S.; Wilson, P. A.; Brown, T. M.; Christensen-Dalsgaard,
J.; Gilliland, R. L.; Kjeldsen, H.; Campante, T. L.; Fletcher, S. T.;
Handberg, R.; Régulo, C.; Salabert, D.; Schou, J.; Verner, G. A.;
Ballot, J.; Broomhall, A. -M.; Elsworth, Y.; Hekker, S.; Huber, D.;
Mathur, S.; New, R.; Roxburgh, I. W.; Sato, K. H.; White, T. R.;
Borucki, W. J.; Koch, D. G.; Jenkins, J. M.
2010ApJ...723.1583M Altcode: 2010arXiv1010.4329M
The primary science goal of the Kepler Mission is to provide
a census of exoplanets in the solar neighborhood, including the
identification and characterization of habitable Earth-like planets. The
asteroseismic capabilities of the mission are being used to determine
precise radii and ages for the target stars from their solar-like
oscillations. Chaplin et al. published observations of three bright
G-type stars, which were monitored during the first 33.5 days of science
operations. One of these stars, the subgiant KIC 11026764, exhibits a
characteristic pattern of oscillation frequencies suggesting that it
has evolved significantly. We have derived asteroseismic estimates of
the properties of KIC 11026764 from Kepler photometry combined with
ground-based spectroscopic data. We present the results of detailed
modeling for this star, employing a variety of independent codes and
analyses that attempt to match the asteroseismic and spectroscopic
constraints simultaneously. We determine both the radius and the age
of KIC 11026764 with a precision near 1%, and an accuracy near 2%
for the radius and 15% for the age. Continued observations of this
star promise to reveal additional oscillation frequencies that will
further improve the determination of its fundamental properties.
---------------------------------------------------------
Title: A comparison of frequentist and Bayesian inference: searching
for low-frequency p modes and g modes in Sun-as-a-star data
Authors: Broomhall, A. -M.; Chaplin, W. J.; Elsworth, Y.; Appourchaux,
T.; New, R.
2010MNRAS.406..767B Altcode: 2010MNRAS.tmp..680B; 2010arXiv1004.4505B
We describe and use two different statistical approaches to
try and detect low-frequency solar oscillations in Sun-as-a-star
data: a frequentist approach and a Bayesian approach. We have used
frequentist statistics to search contemporaneous Sun-as-a-star data
for coincident, statistically prominent features. However, we find
that this approach leads to numerous false detections. We have also
used Bayesian statistics to search for evidence of low-frequency p
modes and g modes in Sun-as-a-star data. We describe how Bayesian
statistics can be used to search near-contemporaneous data for
coincident prominent features. Near-contemporaneous data were
used to circumvent the difficulties in deriving probabilities that
occur when common noise is present in the data. We find that the
Bayesian approach, which is reliant on the assumptions made when
determining the posterior probability, leads to significantly fewer
false detections and those that are observed can be discredited using
a priori knowledge. Therefore, we have more confidence in the mode
candidates found with Bayesian statistics.
---------------------------------------------------------
Title: Possible detection of phase changes from the non-transiting
planet HD 46375b by CoRoT
Authors: Gaulme, P.; Vannier, M.; Guillot, T.; Mosser, B.; Mary,
D.; Weiss, W. W.; Schmider, F. -X.; Bourguignon, S.; Deeg, H. J.;
Régulo, C.; Aigrain, S.; Schneider, J.; Bruntt, H.; Deheuvels, S.;
Donati, J. -F.; Appourchaux, T.; Auvergne, M.; Baglin, A.; Baudin,
F.; Catala, C.; Michel, E.; Samadi, R.
2010A&A...518L.153G Altcode: 2010arXiv1011.2690G
Context. The present work deals with the detection of phase changes
in an exoplanetary system. HD 46375 is a solar analog known to host
a non-transiting Saturn-mass exoplanet with a 3.0236 day period. It
was observed by the CoRoT satellite for 34 days during the fall of
2008. <BR /> Aims: We attempt to identify at optical wavelengths,
the changing phases of the planet as it orbits its star. We then
try to improve the star model by means of a seismic analysis of the
same light curve and the use of ground-based spectropolarimetric
observations. <BR /> Methods: The data analysis relies on the Fourier
spectrum and the folding of the time series. <BR /> Results: We find
evidence of a sinusoidal signal compatible in terms of both amplitude
and phase with light reflected by the planet. Its relative amplitude
is Δ F<SUB>p</SUB>/F<SUB>star</SUB> = [13.0, 26.8] ppm, implying an
albedo A = [0.16, 0.33] or a dayside visible brightness temperature
T<SUB>b</SUB> ≃ [1880, 2030] K by assuming a radius R = 1.1
R<SUB>Jup</SUB> and an inclination i = 45°. Its orbital phase differs
from that of the radial-velocity signal by at most 2 σ_RV. However,
the tiny planetary signal is strongly blended by another signal, which
we attribute to a telluric signal with a 1 day period. We show that
this signal is suppressed, but not eliminated, when using the time
series for HD 46179 from the same CoRoT run as a reference. <BR />
Conclusions: This detection of reflected light from a non-transiting
planet should be confirmable with a longer CoRoT observation of the
same field. In any case, it demonstrates that non-transiting planets
can be characterized using ultra-precise photometric lightcurves
with present-day observations by CoRoT and Kepler. The combined
detection of solar-type oscillations on the same targets (Gaulme et
al. 2010a) highlights the overlap between exoplanetary science and
asteroseismology and shows the high potential of a mission such as
Plato. <P />The CoRoT space mission, launched on 2006 December 27,
was developed and is operated by the CNES, with participation of
the Science Programs of ESA, ESA's RSSD, Austria, Belgium, Brazil,
Germany and Spain.Figure 6 is only available in electronic form at
<A href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: The solar-like CoRoT target HD 170987: spectroscopic and
seismic observations
Authors: Mathur, S.; García, R. A.; Catala, C.; Bruntt, H.; Mosser,
B.; Appourchaux, T.; Ballot, J.; Creevey, O. L.; Gaulme, P.; Hekker,
S.; Huber, D.; Karoff, C.; Piau, L.; Régulo, C.; Roxburgh, I. W.;
Salabert, D.; Verner, G. A.; Auvergne, M.; Baglin, A.; Chaplin, W. J.;
Elsworth, Y.; Michel, E.; Samadi, R.; Sato, K.; Stello, D.
2010A&A...518A..53M Altcode: 2010arXiv1004.4891M
Context. The CoRoT mission is in its third year of observation and the
data from the second long run in the galactic centre direction are being
analysed. The solar-like oscillating stars that have been observed up
to now have given some interesting results, specially concerning the
amplitudes that are lower than predicted. We present here the results
from the analysis of the star HD 170987. <BR /> Aims: The goal of this
research work is to characterise the global parameters of HD 170987. We
look for global seismic parameters such as the mean large separation,
maximum amplitude of the modes, and surface rotation because the
signal-to-noise ratio in the observations does not allow us to measure
individual modes. We also aim to retrieve the parameters of the star
and its chemical composition. <BR /> Methods: We studied the chemical
composition of the star through ground-based observations performed
with the NARVAL spectrograph. We used several methods to calculate
the global parameters from the acoustic oscillations based on CoRoT
data. The light curve of the star has been interpolated with inpainting
algorithms to reduce the effect of data gaps. <BR /> Results: We found
the power excess related to p modes in the range [400-1200] μHz with
a mean large separation of 55.2 ± 0.8 μHz with a probability above
95 % that increases to 55.9 ± 0.2 μHz in a higher frequency range
[500-1250] μHz and a rejection level of 1%. A hint of the variation of
this quantity with frequency was also found. The rotation period of the
star is estimated to be around 4.3 days with an inclination axis of i =
50° <SUP>+20</SUP><SUB>-13</SUB>. We measured a bolometric amplitude
per radial mode in a range [2.4-2.9] ppm around 1000 μHz. Finally
we estimate the stellar mass with a grid of models, M = 1.43 ± 0.05
M_⊙, the radius, R = 1.96 ± 0.046 R_⊙, and the age ~2.4 Gyr. <P
/>The CoRoT space mission, launched on 2006 December 27, has been
developed and is operated by CNES, with the contribution of Austria,
Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain.
---------------------------------------------------------
Title: The technical challenges of the Solar-Orbiter EUI instrument
Authors: Halain, Jean-Philippe; Rochus, Pierre; Appourchaux, Thierry;
Berghmans, David; Harra, Louise; Schühle, Udo; Auchère, Frédéric;
Zhukov, Andrei; Renotte, Etienne; Defise, Jean-Marc; Rossi, Laurence;
Fleury-Frenette, Karl; Jacques, Lionel; Hochedez, Jean-François;
Ben Moussa, Ali
2010SPIE.7732E..0RH Altcode: 2010SPIE.7732E..20H
The Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter consists of
a suite of two high-resolution imagers (HRI) and one dual-band full
Sun imager (FSI) that will provide EUV and Lyman-α images of the
solar atmospheric layers above the photosphere. The EUI instrument is
based on a set of challenging new technologies allowing to reach the
scientific objectives and to cope with the hard space environment of
the Solar Orbiter mission. The mechanical concept of the EUI instrument
is based on a common structure supporting the HRI and FSI channels,
and a separated electronic box. A heat rejection baffle system is
used to reduce the Sun heat load and provide a first protection level
against the solar disk straylight. The spectral bands are selected by
thin filters and multilayer mirror coatings. The detectors are 10μm
pitch back illuminated CMOS Active Pixel Sensors (APS), best suited
for the EUI science requirements and radiation hardness. This paper
presents the EUI instrument concept and its major sub-systems. The
current developments of the instrument technologies are also summarized.
---------------------------------------------------------
Title: Definition of an imaging spectrometer meeting the needs of
UV solar physics
Authors: Ruiz de Galarreta Fanjul, C.; Philippon, A.; Vial, J. -C.;
Lemaire, P.; Maillard, J. -P.; Buisset, C.; Appourchaux, T.;
Auchère, F.
2010SPIE.7732E..36R Altcode: 2010SPIE.7732E..99R
The study of the outer solar atmosphere requires combining imaging
and spectroscopy in the UV lines formed in the high chromosphere,
the transition region and the corona. We start from the science
requirements and we define the instrumental specifications in terms
of field-of-view (FOV), spatial, temporal and spectral resolution and
bandpass. We propose two different all-reflection optical architectures
based on interferometric techniques: Spatial Heterodyne Spectroscopy
(SHS); and Imaging Transform Spectrometer (IFTS). We describe the
different set-ups and compare the potential performances of the two
types of solutions, and discuss their feasibility. We conclude that
IFTS appears to be the best solution, meeting the needs of UV solar
physics. However, we point out the many difficulties to be encountered,
especially as far as metrology is concerned.
---------------------------------------------------------
Title: Seismic and spectroscopic characterization of the solar-like
pulsating CoRoT target HD 49385
Authors: Deheuvels, S.; Bruntt, H.; Michel, E.; Barban, C.; Verner,
G.; Régulo, C.; Mosser, B.; Mathur, S.; Gaulme, P.; Garcia, R. A.;
Boumier, P.; Appourchaux, T.; Samadi, R.; Catala, C.; Baudin, F.;
Baglin, A.; Auvergne, M.; Roxburgh, I. W.; Pérez Hernández, F.
2010A&A...515A..87D Altcode: 2010arXiv1003.4368D
Context. The star HD 49385 is the first G-type solar-like pulsator
observed in the seismology field of the space telescope CoRoT. The
satellite collected 137 days of high-precision photometric data on
this star, confirming that it presents solar-like oscillations. HD
49385 was also observed in spectroscopy with the NARVAL spectrograph in
January 2009. <BR /> Aims: Our goal is to characterize HD 49385 using
both spectroscopic and seismic data. <BR /> Methods: The fundamental
stellar parameters of HD 49385 are derived with the semi-automatic
software VWA, and the projected rotational velocity is estimated by
fitting synthetic profiles to isolated lines in the observed spectrum. A
maximum likelihood estimation is used to determine the parameters of
the observed p modes. We perform a global fit, in which modes are fitted
simultaneously over nine radial orders, with degrees ranging from ℓ =
0 to ℓ = 3 (36 individual modes). <BR /> Results: Precise estimates of
the atmospheric parameters (T<SUB>eff</SUB>, [M/H], log g) and of the ν
sin i of HD 49385 are obtained. The seismic analysis of the star leads
to a clear identification of the modes for degrees ℓ = 0,1,2. Around
the maximum of the signal (ν ≃ 1013 μHz), some peaks are found
significant and compatible with the expected characteristics of ℓ =
3 modes. Our fit yields robust estimates of the frequencies, linewidths
and amplitudes of the modes. We find amplitudes of ~5.6 ± 0.8 ppm for
radial modes at the maximum of the signal. The lifetimes of the modes
range from one day (at high frequency) to a bit more than two days
(at low frequency). Significant peaks are found outside the identified
ridges and are fitted. They are attributed to mixed modes. <P />Based
on data obtained from the CoRoT (Convection, Rotation and planetary
Transits) space mission, developed by the French Space agency CNES
in collaboration with the Science Programs of ESA, Austria, Belgium,
Brazil, Germany and Spain.Based on data obtained using the Télescope
Bernard Lyot at Observatoire du Pic du Midi, CNRS and Université Paul
Sabatier, France.
---------------------------------------------------------
Title: An automated pipeline for asteroseismology based on the
autocorrelation of stellar time series
Authors: Mosser, Benoit; Appourchaux, Thierry
2010arXiv1006.5079M Altcode:
The autocorrelation of an asteroseismic time series has been identified
as a powerful tool capable of providing measurements of the large
frequency separations. The performance of this method has been assessed
and quantified by Mosser & Appourchaux (2009). We propose now an
automated pipeline based on it and describe its performance.
---------------------------------------------------------
Title: A Multi-Site Campaign to Measure Solar-Like Oscillations in
Procyon. II. Mode Frequencies
Authors: Bedding, Timothy R.; Kjeldsen, Hans; Campante, Tiago L.;
Appourchaux, Thierry; Bonanno, Alfio; Chaplin, William J.; Garcia,
Rafael A.; Martić, Milena; Mosser, Benoit; Butler, R. Paul; Bruntt,
Hans; Kiss, László L.; O'Toole, Simon J.; Kambe, Eiji; Ando,
Hiroyasu; Izumiura, Hideyuki; Sato, Bun'ei; Hartmann, Michael;
Hatzes, Artie; Barban, Caroline; Berthomieu, Gabrielle; Michel,
Eric; Provost, Janine; Turck-Chièze, Sylvaine; Lebrun, Jean-Claude;
Schmitt, Jerome; Bertaux, Jean-Loup; Benatti, Serena; Claudi, Riccardo
U.; Cosentino, Rosario; Leccia, Silvio; Frandsen, Søren; Brogaard,
Karsten; Glowienka, Lars; Grundahl, Frank; Stempels, Eric; Arentoft,
Torben; Bazot, Michaël; Christensen-Dalsgaard, Jørgen; Dall, Thomas
H.; Karoff, Christoffer; Lundgreen-Nielsen, Jens; Carrier, Fabien;
Eggenberger, Patrick; Sosnowska, Danuta; Wittenmyer, Robert A.; Endl,
Michael; Metcalfe, Travis S.; Hekker, Saskia; Reffert, Sabine
2010ApJ...713..935B Altcode: 2010arXiv1003.0052B
We have analyzed data from a multi-site campaign to observe oscillations
in the F5 star Procyon. The data consist of high-precision velocities
that we obtained over more than three weeks with 11 telescopes. A
new method for adjusting the data weights allows us to suppress the
sidelobes in the power spectrum. Stacking the power spectrum in a
so-called échelle diagram reveals two clear ridges, which we identify
with even and odd values of the angular degree (l = 0 and 2, and l =
1 and 3, respectively). We interpret a strong, narrow peak at 446 μHz
that lies close to the l = 1 ridge as a mode with mixed character. We
show that the frequencies of the ridge centroids and their separations
are useful diagnostics for asteroseismology. In particular, variations
in the large separation appear to indicate a glitch in the sound-speed
profile at an acoustic depth of ~1000 s. We list frequencies for 55
modes extracted from the data spanning 20 radial orders, a range
comparable to the best solar data, which will provide valuable
constraints for theoretical models. A preliminary comparison with
published models shows that the offset between observed and calculated
frequencies for the radial modes is very different for Procyon than
for the Sun and other cool stars. We find the mean lifetime of the
modes in Procyon to be 1.29<SUP>+0.55</SUP> <SUB>-0.49</SUB> days,
which is significantly shorter than the 2-4 days seen in the Sun.
---------------------------------------------------------
Title: The Asteroseismic Potential of Kepler: First Results for
Solar-Type Stars
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; García,
R. A.; Houdek, G.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz,
J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Brown, T. M.;
Christensen-Dalsgaard, J.; Gilliland, R. L.; Kjeldsen, H.; Borucki,
W. J.; Koch, D.; Jenkins, J. M.; Ballot, J.; Basu, S.; Bazot, M.;
Bedding, T. R.; Benomar, O.; Bonanno, A.; Brandão, I. M.; Bruntt,
H.; Campante, T. L.; Creevey, O. L.; Di Mauro, M. P.; Doǧan,
G.; Dreizler, S.; Eggenberger, P.; Esch, L.; Fletcher, S. T.;
Frandsen, S.; Gai, N.; Gaulme, P.; Handberg, R.; Hekker, S.; Howe,
R.; Huber, D.; Korzennik, S. G.; Lebrun, J. C.; Leccia, S.; Martic,
M.; Mathur, S.; Mosser, B.; New, R.; Quirion, P. -O.; Régulo, C.;
Roxburgh, I. W.; Salabert, D.; Schou, J.; Sousa, S. G.; Stello, D.;
Verner, G. A.; Arentoft, T.; Barban, C.; Belkacem, K.; Benatti, S.;
Biazzo, K.; Boumier, P.; Bradley, P. A.; Broomhall, A. -M.; Buzasi,
D. L.; Claudi, R. U.; Cunha, M. S.; D'Antona, F.; Deheuvels, S.;
Derekas, A.; García Hernández, A.; Giampapa, M. S.; Goupil, M. J.;
Gruberbauer, M.; Guzik, J. A.; Hale, S. J.; Ireland, M. J.; Kiss,
L. L.; Kitiashvili, I. N.; Kolenberg, K.; Korhonen, H.; Kosovichev,
A. G.; Kupka, F.; Lebreton, Y.; Leroy, B.; Ludwig, H. -G.; Mathis, S.;
Michel, E.; Miglio, A.; Montalbán, J.; Moya, A.; Noels, A.; Noyes,
R. W.; Pallé, P. L.; Piau, L.; Preston, H. L.; Roca Cortés, T.;
Roth, M.; Sato, K. H.; Schmitt, J.; Serenelli, A. M.; Silva Aguirre,
V.; Stevens, I. R.; Suárez, J. C.; Suran, M. D.; Trampedach, R.;
Turck-Chièze, S.; Uytterhoeven, K.; Ventura, R.; Wilson, P. A.
2010ApJ...713L.169C Altcode: 2010arXiv1001.0506C
We present preliminary asteroseismic results from Kepler on three G-type
stars. The observations, made at one-minute cadence during the first
33.5 days of science operations, reveal high signal-to-noise solar-like
oscillation spectra in all three stars: about 20 modes of oscillation
may be clearly distinguished in each star. We discuss the appearance of
the oscillation spectra, use the frequencies and frequency separations
to provide first results on the radii, masses, and ages of the stars,
and comment in the light of these results on prospects for inference
on other solar-type stars that Kepler will observe.
---------------------------------------------------------
Title: Kepler Asteroseismology Program: Introduction and First Results
Authors: Gilliland, Ronald L.; Brown, Timothy M.;
Christensen-Dalsgaard, Jørgen; Kjeldsen, Hans; Aerts, Conny;
Appourchaux, Thierry; Basu, Sarbani; Bedding, Timothy R.; Chaplin,
William J.; Cunha, Margarida S.; De Cat, Peter; De Ridder, Joris;
Guzik, Joyce A.; Handler, Gerald; Kawaler, Steven; Kiss, László;
Kolenberg, Katrien; Kurtz, Donald W.; Metcalfe, Travis S.; Monteiro,
Mario J. P. F. G.; Szabó, Robert; Arentoft, Torben; Balona, Luis;
Debosscher, Jonas; Elsworth, Yvonne P.; Quirion, Pierre-Olivier;
Stello, Dennis; Suárez, Juan Carlos; Borucki, William J.; Jenkins,
Jon M.; Koch, David; Kondo, Yoji; Latham, David W.; Rowe, Jason F.;
Steffen, Jason H.
2010PASP..122..131G Altcode: 2010arXiv1001.0139G
Asteroseismology involves probing the interiors of stars and quantifying
their global properties, such as radius and age, through observations of
normal modes of oscillation. The technical requirements for conducting
asteroseismology include ultrahigh precision measured in photometry
in parts per million, as well as nearly continuous time series over
weeks to years, and cadences rapid enough to sample oscillations with
periods as short as a few minutes. We report on results from the first
43 days of observations, in which the unique capabilities of Kepler
in providing a revolutionary advance in asteroseismology are already
well in evidence. The Kepler asteroseismology program holds intrinsic
importance in supporting the core planetary search program through
greatly enhanced knowledge of host star properties, and extends well
beyond this to rich applications in stellar astrophysics.
---------------------------------------------------------
Title: The quest for the solar g modes
Authors: Appourchaux, T.; Belkacem, K.; Broomhall, A. -M.; Chaplin,
W. J.; Gough, D. O.; Houdek, G.; Provost, J.; Baudin, F.; Boumier,
P.; Elsworth, Y.; García, R. A.; Andersen, B. N.; Finsterle, W.;
Fröhlich, C.; Gabriel, A.; Grec, G.; Jiménez, A.; Kosovichev, A.;
Sekii, T.; Toutain, T.; Turck-Chièze, S.
2010A&ARv..18..197A Altcode: 2010A&ARv.tmp....1A; 2009arXiv0910.0848A
Solar gravity modes (or g modes)—oscillations of the solar interior
on which buoyancy acts as the restoring force—have the potential
to provide unprecedented inference on the structure and dynamics of
the solar core, inference that is not possible with the well-observed
acoustic modes (or p modes). The relative high amplitude of the g-mode
eigenfunctions in the core and the evanesence of the modes in the
convection zone make the modes particularly sensitive to the physical
and dynamical conditions in the core. Owing to the existence of the
convection zone, the g modes have very low amplitudes at photospheric
levels, which makes the modes extremely hard to detect. In this article,
we review the current state of play regarding attempts to detect g
modes. We review the theory of g modes, including theoretical estimation
of the g-mode frequencies, amplitudes and damping rates. Then we go
on to discuss the techniques that have been used to try to detect g
modes. We review results in the literature, and finish by looking to
the future, and the potential advances that can be made—from both
data and data-analysis perspectives—to give unambiguous detections
of individual g modes. The review ends by concluding that, at the time
of writing, there is indeed a consensus amongst the authors that there
is currently no undisputed detection of solar g modes.
---------------------------------------------------------
Title: The CoRoT target HD 49933 . II. Comparison of theoretical
mode amplitudes with observations
Authors: Samadi, R.; Ludwig, H. -G.; Belkacem, K.; Goupil, M. J.;
Benomar, O.; Mosser, B.; Dupret, M. -A.; Baudin, F.; Appourchaux,
T.; Michel, E.
2010A&A...509A..16S Altcode: 2009arXiv0910.4037S
Context. The seismic data obtained by CoRoT for the star HD 49933 enable
us for the first time to measure directly the amplitudes and linewidths
of solar-like oscillations for a star other than the Sun. From those
measurements it is possible, as was done for the Sun, to constrain
models of the excitation of acoustic modes by turbulent convection. <BR
/> Aims: We compare a stochastic excitation model described in Paper
I with the asteroseismology data for HD 49933, a star that is rather
metal poor and significantly hotter than the Sun. <BR /> Methods:
Using the seismic determinations of the mode linewidths detected by
CoRoT for HD 49933 and the theoretical mode excitation rates computed
in Paper I for the specific case of HD 49933, we derive the expected
surface velocity amplitudes of the acoustic modes detected in HD
49933. Using a calibrated quasi-adiabatic approximation relating
the mode amplitudes in intensity to those in velocity, we derive the
expected values of the mode amplitude in intensity. <BR /> Results:
Except at rather high frequency, our amplitude calculations are within
1-σ error bars of the mode surface velocity spectrum derived with
the HARPS spectrograph. The same is found with respect to the mode
amplitudes in intensity derived for HD 49933 from the CoRoT data. On
the other hand, at high frequency (ν ⪆ 1.9 mHz), our calculations
depart significantly from the CoRoT and HARPS measurements. We show
that assuming a solar metal abundance rather than the actual metal
abundance of the star would result in a larger discrepancy with the
seismic data. Furthermore, we present calculations which assume the
“new” solar chemical mixture to be in better agreement with the
seismic data than those that assumed the “old” solar chemical
mixture. <BR /> Conclusions: These results validate in the case of a
star significantly hotter than the Sun and α Cen A the main assumptions
in the model of stochastic excitation. However, the discrepancies seen
at high frequency highlight some deficiencies of the modelling, whose
origin remains to be understood. We also show that it is important
to take the surface metal abundance of the solar-like pulsators into
account. <P />The CoRoT space mission, launched on December 27 2006,
has been developped and is operated by CNES, with the contribution of
Austria, Belgium, Brasil, ESA, Germany and Spain.
---------------------------------------------------------
Title: SIAMOIS, asteroseismolgy at Dome C after CoRoT
Authors: Mosser, B.; Buey, T.; Appourchaux, T.; Charpinet, S.; Mathias,
P.; Schmider, F. X.; Maillard, J. P.; Siamois Team
2010EAS....40..381M Altcode:
SIAMOIS is a ground-based asteroseismology project, to pursue velocity
measurements from the Dome C Concordia station in Antarctica. Dome
C appears to be the ideal place for ground-based asteroseismic
observations as it is capable of delivering a duty cycle as high as
87% during the three-month long polar night. This high duty cycle,
a crucial point for asteroseismology, is comparable to the best
space-borne observations. We present the quality of the SIAMOIS project,
that yields to its selection as top priority by the working group of
ARENA dedicated to “Time series observations from Dome C”. We
show that, after CoRoT, SIAMOIS proposes a large scientific case,
that extends the pioneering work and great discoveries of CoRoT. We
depict a few important ingredients of the project: full automation,
space-like philosophy, and compatibility with the current facilities at
the Concordia station. SIAMOIS has no real competitor before at least
2016/2017, and can be considered as a pathfinder for many important
issues concerning astronomical observations at Dome C.
---------------------------------------------------------
Title: On detecting the large separation in the autocorrelation of
stellar oscillation times series
Authors: Mosser, B.; Appourchaux, T.
2009A&A...508..877M Altcode: 2009arXiv0909.0782M
Context: The observations carried out by the space missions CoRoT
and Kepler provide a large set of asteroseismic data. Their analysis
requires an efficient procedure first to determine if a star reliably
shows solar-like oscillations, second to measure the so-called large
separation, third to estimate the asteroseismic information that can
be retrieved from the Fourier spectrum.<BR /> Aims: In this paper we
develop a procedure based on the autocorrelation of the seismic Fourier
spectrum that is capable of providing measurements of the large and
small frequency separations. The performance of the autocorrelation
method needs to be assessed and quantified. We therefore searched
for criteria able to predict the output that one can expect from the
analysis by autocorrelation of a seismic time series. <BR /> Methods:
First, the autocorrelation is properly scaled to take into account
the contribution of white noise. Then we use the null hypothesis
H<SUB>0</SUB> test to assess the reliability of the autocorrelation
analysis. Calculations based on solar and CoRoT time series are
performed to quantify the performance as a function of the amplitude
of the autocorrelation signal.<BR /> Results: We obtain an empirical
relation for the performance of the autocorrelation method. We show
that the precision of the method increases with the observation
length, and with the mean seismic amplitude-to-background ratio of
the pressure modes to the power 1.5 ± 0.05. We propose an automated
determination of the large separation, whose reliability is quantified
by the H<SUB>0</SUB> test. We apply this method to analyze red giants
observed by CoRoT. We estimate the expected performance for photometric
time series of the Kepler mission. We demonstrate that the method
makes it possible to distinguish ℓ = 0 from ℓ = 1 modes.<BR />
Conclusions: The envelope autocorrelation function (EACF) has proven
to be very powerful for the determination of the large separation
in noisy asteroseismic data, since it enables us to quantify the
precision of the performance of different measurements: mean large
separation, variation of the large separation with frequency, small
separation and degree identification. <P />The CoRoT space mission,
launched on 2006 December 27, was developed and is operated by the
CNES, with participation of the Science Programs of ESA, ESA's RSSD,
Austria, Belgium, Brazil, Germany and Spain.
---------------------------------------------------------
Title: A fresh look at the seismic spectrum of HD49933: analysis of
180 days of CoRoT photometry
Authors: Benomar, O.; Baudin, F.; Campante, T. L.; Chaplin, W. J.;
García, R. A.; Gaulme, P.; Toutain, T.; Verner, G. A.; Appourchaux,
T.; Ballot, J.; Barban, C.; Elsworth, Y.; Mathur, S.; Mosser, B.;
Régulo, C.; Roxburgh, I. W.; Auvergne, M.; Baglin, A.; Catala, C.;
Michel, E.; Samadi, R.
2009A&A...507L..13B Altcode: 2009arXiv0910.3060B
Context: Solar-like oscillations have now been observed in several
stars, thanks to ground-based spectroscopic observations and space-borne
photometry. CoRoT, which has been in orbit since December 2006, has
observed the star HD49933 twice. The oscillation spectrum of this
star has proven difficult to interpret. <BR />Aims: Thanks to a new
timeseries provided by CoRoT, we aim to provide a robust description
of the oscillations in HD49933, i.e., to identify the degrees of the
observed modes, and to measure mode frequencies, widths, amplitudes
and the average rotational splitting. <BR />Methods: Several methods
were used to model the Fourier spectrum: Maximum Likelihood Estimators
and Bayesian analysis using Markov Chain Monte-Carlo techniques. <BR
/>Results: The different methods yield consistent result, and allow us
to make a robust identification of the modes and to extract precise
mode parameters. Only the rotational splitting remains difficult to
estimate precisely, but is clearly relatively large (several μHz in
size). <P />The CoRoT space mission, launched on 2006 December 27,
was developed and is operated by the CNES, with participation of
the Science Programs of ESA, ESA's RSSD, Austria, Belgium, Brazil,
Germany and Spain. <P />Figures 5-9 and Table 2 are only available in
electronic form at http://www.aanda.org
---------------------------------------------------------
Title: The solar-like oscillations of HD 49933: a Bayesian approach
Authors: Benomar, O.; Appourchaux, T.; Baudin, F.
2009A&A...506...15B Altcode:
Context: Asteroseismology has entered a new era with the availability
of continuous observations from space-borne missions such as MOST,
CoRoT and Kepler. However, the low amplitude and the complexity
of the observed spectrum make the exploitation of these data sets
difficult. <BR />Aims: The use of robust methods to estimate the
parameters of stellar oscillation eigenmodes is necessary to fully
exploit these new data sets. These parameters include in particular
the frequency, the width and the energy of the eigenmodes, all
being required for a seismic interpretation of the stellar internal
structure or excitation of the eigenmodes. <BR />Methods: A Bayesian
approach, coupled with a Markov chain Monte Carlo (MCMC) algorithm, is
presented. Such a method allows the use of a priori knowledge to improve
the parameter estimation. It also provides complete information on the
probability distribution of the fitted parameters. The method is tested
on simulated time series and then applied to CoRoT observations of HD
49933. <BR />Results: The simulated time series allow the validation
of the method for conditions similar to those of the observations in
terms of spectral complexity and signal-to-noise ratio. However, a very
important problem in the analysis of the HD 49933 mode spectrum is the
l degree identification of the modes. The degree identification has
little impact on the large frequency separation, rotational splitting,
energy and width estimation, whereas individual frequencies and the star
inclination angle evaluation are strongly affected. From a statistical
point of view, we provide a quantitative ranking of the four models
considered. The most probable model includes only modes of degree 0
and 1. Two other models include modes with degree up to 2 and have a
non negligible level of significance. The last model includes modes of
degree 0 and 1 but has an alternate degree identification and can be
definitively rejected. In conclusion, the significance of the resulting
probabilities is not sufficient to draw a definite conclusion. <P />The
CoRoT space mission, launched on <P />2006 December 27, was developed
and is operated by the CNES, with <P />participation of the Science
Programs of ESA, ESA's RSSD, Austria, <P />Belgium, Brazil, Germany
and Spain. <P />Tables 10 to 15 and Figs. 11, 12 are only available
in electronic form at http://www.aanda.org
---------------------------------------------------------
Title: The CoRoT target HD 175726: an active star with weak solar-like
oscillations
Authors: Mosser, B.; Michel, E.; Appourchaux, T.; Barban, C.; Baudin,
F.; Boumier, P.; Bruntt, H.; Catala, C.; Deheuvels, S.; García,
R. A.; Gaulme, P.; Regulo, C.; Roxburgh, I.; Samadi, R.; Verner, G.;
Auvergne, M.; Baglin, A.; Ballot, J.; Benomar, O.; Mathur, S.
2009A&A...506...33M Altcode: 2009arXiv0908.2244M
Context: The CoRoT short runs give us the opportunity to observe a large
variety of late-type stars through their solar-like oscillations. We
report observations of the star HD 175726 that lasted for 27 days
during the first short run of the mission. The time series reveals a
high-activity signal and the power spectrum presents an excess due to
solar-like oscillations with a low signal-to-noise ratio. <BR />Aims:
Our aim is to identify the most efficient tools to extract as much
information as possible from the power density spectrum. <BR />Methods:
The most productive method appears to be the autocorrelation of the
time series, calculated as the spectrum of the filtered spectrum. This
method is efficient, very rapid computationally, and will be useful for
the analysis of other targets, observed with CoRoT or with forthcoming
missions such as Kepler and Plato. <BR />Results: The mean large
separation has been measured to be 97.2±0.5 μHz, slightly below the
expected value determined from solar scaling laws. We also show strong
evidence for variation of the large separation with frequency. The
bolometric mode amplitude is only 1.7±0.25 ppm for radial modes, which
is 1.7 times less than expected. Due to the low signal-to-noise ratio,
mode identification is not possible for the available data set of HD
175726. <P />The CoRoT space mission, launched on 2006 December 27, was
developed and is operated by the CNES, with participation of the Science
Programs of ESA, ESAs RSSD, Austria, Belgium, Brazil, Germany and Spain.
---------------------------------------------------------
Title: Mode width fitting with a simple Bayesian approach. Application
to CoRoT targets HD 181420 and HD 49933
Authors: Gaulme, P.; Appourchaux, T.; Boumier, P.
2009A&A...506....7G Altcode: 2010arXiv1011.2675G
Aims: We investigate the asteroseismology of two solar-like targets as
observed with the CoRoT satellite, with particular attention paid to
the mode fitting. HD 181420 and HD 49933 are typical CoRoT solar-like
targets (156 and 60-day runs). The low signal-to-noise ratio (SNR) of
about 3{-}10 prevents us from unambiguously identifying the individual
oscillation modes. In particular, convergence problems appear at the
edges of the oscillation spectrum. <BR />Methods: We apply a Bayesian
approach to the analysis of these data. We compare the global fitting
of the power spectra obtained by the classical maximum likelihood
(MLE) and the maximum a posteriori (MAP) estimators. <BR />Results:
We examine the impact of the choice of the priors upon the fitted
parameters. We also propose to reduce the number of free parameters
in the fitting, by replacing the individual estimate of mode height
associated with each overtone by a continuous function of frequency
(Gaussian profile). <BR />Conclusions: The MAP appears as a powerful
tool to constrain the global fits, but it must be used carefully and
only with reliable priors. The mode width of the stars increases with
the frequency over all the oscillation spectrum. <P />The CoRoT space
mission, launched on 2006 December 27, was developed and is operated
by the CNES, with participation of the Science Programs of ESA, ESA's
RSSD, Austria, Belgium, Brazil, Germany and Spain.
---------------------------------------------------------
Title: On posterior probability and significance level: application
to the power spectrum of HD 49 933 observed by CoRoT
Authors: Appourchaux, T.; Samadi, R.; Dupret, M. -A.
2009A&A...506....1A Altcode: 2009arXiv0906.0864A
Context: The CoRoT mission provides asteroseismic data of very high
quality allowing one to adopt new statistical approaches for mode
detection in power spectra, especially with respect to testing the
null hypothesis (H{0}, which assumes that what is observed is pure
noise). <BR />Aims: We emphasize that the significance level when
rejecting the null hypothesis can lead to the incorrect conclusion
that the H{0} hypothesis is unlikely to occur at that significance
level. We demonstrate that the significance level is unrelated to
the posterior probability of H{0}, given the observed data set, and
that this posterior probability is very much higher than implied
by the significance level. <BR />Methods: We use Bayes theorem to
derive the posterior probability of that H{0} is true assuming an
alternative hypothesis H{1} that a mode is present, taking some prior
for the mode height, mode amplitude and linewidth. <BR />Results: We
compute the posterior probability of H{0} for the p modes detected on
HD 49 933 by CoRoT. <BR />Conclusions: We conclude that the posterior
probability of H{0} provide a much more conservative quantification
of the mode detection than the significance level. This framework
can be applied to any similar stellar power spectra obtained to
complete asteroseismology. <P />The CoRoT space mission, launched
on <P />2006 December 27, was developed and is operated by the CNES,
with <P />participation of the Science Programs of ESA, ESA's RSSD,
Austria, <P />Belgium, Brazil, Germany and Spain.
---------------------------------------------------------
Title: The CoRoT satellite in flight: description and performance
Authors: Auvergne, M.; Bodin, P.; Boisnard, L.; Buey, J. -T.;
Chaintreuil, S.; Epstein, G.; Jouret, M.; Lam-Trong, T.; Levacher,
P.; Magnan, A.; Perez, R.; Plasson, P.; Plesseria, J.; Peter, G.;
Steller, M.; Tiphène, D.; Baglin, A.; Agogué, P.; Appourchaux,
T.; Barbet, D.; Beaufort, T.; Bellenger, R.; Berlin, R.; Bernardi,
P.; Blouin, D.; Boumier, P.; Bonneau, F.; Briet, R.; Butler, B.;
Cautain, R.; Chiavassa, F.; Costes, V.; Cuvilho, J.; Cunha-Parro,
V.; de Oliveira Fialho, F.; Decaudin, M.; Defise, J. -M.; Djalal, S.;
Docclo, A.; Drummond, R.; Dupuis, O.; Exil, G.; Fauré, C.; Gaboriaud,
A.; Gamet, P.; Gavalda, P.; Grolleau, E.; Gueguen, L.; Guivarc'h,
V.; Guterman, P.; Hasiba, J.; Huntzinger, G.; Hustaix, H.; Imbert,
C.; Jeanville, G.; Johlander, B.; Jorda, L.; Journoud, P.; Karioty,
F.; Kerjean, L.; Lafond, L.; Lapeyrere, V.; Landiech, P.; Larqué,
T.; Laudet, P.; Le Merrer, J.; Leporati, L.; Leruyet, B.; Levieuge,
B.; Llebaria, A.; Martin, L.; Mazy, E.; Mesnager, J. -M.; Michel,
J. -P.; Moalic, J. -P.; Monjoin, W.; Naudet, D.; Neukirchner, S.;
Nguyen-Kim, K.; Ollivier, M.; Orcesi, J. -L.; Ottacher, H.; Oulali,
A.; Parisot, J.; Perruchot, S.; Piacentino, A.; Pinheiro da Silva,
L.; Platzer, J.; Pontet, B.; Pradines, A.; Quentin, C.; Rohbeck, U.;
Rolland, G.; Rollenhagen, F.; Romagnan, R.; Russ, N.; Samadi, R.;
Schmidt, R.; Schwartz, N.; Sebbag, I.; Smit, H.; Sunter, W.; Tello,
M.; Toulouse, P.; Ulmer, B.; Vandermarcq, O.; Vergnault, E.; Wallner,
R.; Waultier, G.; Zanatta, P.
2009A&A...506..411A Altcode: 2009arXiv0901.2206A
Context: CoRoT is a space telescope dedicated to stellar seismology
and the search for extrasolar planets. The mission is led by the CNES
in association with French laboratories and has a large international
participation. The European Space Agency (ESA), Austria, Belgium, and
Germany contribute to the payload, and Spain and Brazil contribute to
the ground segment. Development of the spacecraft, which is based on a
PROTEUS low earth orbit (LEO) recurrent platform, commenced in October
2000, and the satellite was launched on December 27, 2006. <BR />Aims:
The instrument and platform characteristics prior to launch have been
described in ESA publication (SP-1306). In the present paper we explain
the behaviour in flight, based on raw and corrected data. <BR />Methods:
Five runs have been completed since January 2007. The data used here
are essentially those acquired during the commissioning phase and from
a long run that lasted 146 days. These enable us to give a complete
overview of the instrument and platform behaviour for all environmental
conditions. The ground based data processing is not described in detail
because the most important method has been published elsewhere. <BR
/>Results: We show that the performance specifications are easily
satisfied when the environmental conditions are favourable. Most of the
perturbations, hence data corrections, are related to LEO perturbations:
high energy particles inside the South Atlantic Anomaly (SAA), eclipses
and temperature variations, and line of sight fluctuations due to the
attitude control system. Straylight due to the reflected light from
the earth, which is controlled by the telescope and baffle design,
appears to be negligible. <P />The CoRoT space mission, launched on
December 27th 2006, has been developed and is operated by CNES, with
contributions from Austria, Belgium, Brazil, ESA, Germany and Spain. <P
/>Four French laboratories associated with the CNRS (LESIA, LAM, IAS,
OMP) collaborate with CNES on the satellite development. The authors
are grateful to Ian Roxburgh for a careful reading of the manuscript.
---------------------------------------------------------
Title: Hydrodynamical simulations of convection-related stellar
micro-variability. II. The enigmatic granulation background of the
CoRoT target HD 49933
Authors: Ludwig, H. -G.; Samadi, R.; Steffen, M.; Appourchaux, T.;
Baudin, F.; Belkacem, K.; Boumier, P.; Goupil, M. -J.; Michel, E.
2009A&A...506..167L Altcode: 2009arXiv0905.2695L
Context: Local-box hydrodynamical model atmospheres provide
statistical information about a star's emergent radiation field
which allows one to predict the level of its granulation-related
micro-variability. Space-based photometry is now sufficiently
accurate to test model predictions. <BR />Aims: We aim to model the
photometric granulation background of HD 49933 as well as the Sun,
and compare the predictions to the measurements obtained by the
<sf>CoRoT</sf> and <sf>SOHO</sf> satellite
missions. <BR />Methods: We construct hydrodynamical model atmospheres
representing HD 49933 and the Sun, and use a previously developed
scaling technique to obtain the observable disk-integrated brightness
fluctuations. We further performed exploratory magneto-hydrodynamical
simulations to gauge the impact of small scale magnetic fields
on the synthetic light-curves. <BR />Results: We find that the
granulation-related brightness fluctuations depend on metallicity. We
obtain a satisfactory correspondence between prediction and observation
for the Sun, validating our approach. For HD 49933, we arrive at
a significant over-estimation by a factor of two to three in total
power. Locally generated magnetic fields are unlikely to be responsible,
otherwise existing fields would need to be rather strong to sufficiently
suppress the granulation signal. Presently suggested updates on the
fundamental stellar parameters do not improve the correspondence;
however, an ad-hoc increase of the HD 49933 surface gravity by about
0.2 dex would eliminate most of the discrepancy. <BR />Conclusions:
We diagnose a puzzling discrepancy between the predicted and observed
granulation background in HD 49933, with only rather ad-hoc ideas for
remedies at hand. <P />The <sf>CoRoT</sf> space mission,
launched on December 27th 2006, has been developed and is operated by
CNES, with the contribution of Austria, Belgium, Brazil, ESA, Germany
and Spain. CIFIST Marie Curie Excellence Team.
---------------------------------------------------------
Title: Solar-like oscillations in HD 181420: data analysis of 156
days of CoRoT data
Authors: Barban, C.; Deheuvels, S.; Baudin, F.; Appourchaux, T.;
Auvergne, M.; Ballot, J.; Boumier, P.; Chaplin, W. J.; García,
R. A.; Gaulme, P.; Michel, E.; Mosser, B.; Régulo, C.; Roxburgh,
I. W.; Verner, G.; Baglin, A.; Catala, C.; Samadi, R.; Bruntt, H.;
Elsworth, Y.; Mathur, S.
2009A&A...506...51B Altcode:
Context: The estimate of solar-like oscillation properties, such
as their frequencies, amplitudes and lifetimes, is challenging
because of their low amplitudes and will benefit from long and
uninterrupted observing runs. The space telescope CoRoT allows us
to obtain high-performance photometric data over a long and quasi
continuous period. Among its main targets are stars for which we expect
solar-like oscillations. <BR />Aims: HD 181420, an F2 main sequence
star, has been observed by CoRoT during its first long run covering
about 156 days. With this unprecedently high-quality set of data,
our aim is to derive the p-mode parameters that can be used to probe
the stellar interior. <BR />Methods: The CoRoT data obtained on HD
181420 is analysed using a classical Fourier approach for the search
for the p mode signature. The p-mode parameters are then derived using
global fitting of the power spectrum by a Lorentzian model, as used
widely in the solar case. <BR />Results: From the p-mode frequencies,
the mean value of the large spacing is estimated to be 75 {μ Hz}. The
p-mode amplitudes are slightly less than 4 ppm with a line width of
about 8 {μ Hz} at the maximum of the p modes. The inclination angle is
estimated to be around 45 °. The large mode line-width combined with
the observed mode spacing make it difficult to identify the ℓ=2 modes
and to estimate the rotational splitting. We explore two scenarios
for the identification of the modes. <P />The CoRoT space mission,
launched on 2006 December 27, was delopped and is operated by the
CNES with participation of the Science Programs of ESA; ESA's RSSD,
Austria, Belgium, Brazil, Germany and Spain.
---------------------------------------------------------
Title: Solar-like oscillations with low amplitude in the CoRoT target
HD 181906
Authors: García, R. A.; Régulo, C.; Samadi, R.; Ballot, J.; Barban,
C.; Benomar, O.; Chaplin, W. J.; Gaulme, P.; Appourchaux, T.; Mathur,
S.; Mosser, B.; Toutain, T.; Verner, G. A.; Auvergne, M.; Baglin,
A.; Baudin, F.; Boumier, P.; Bruntt, H.; Catala, C.; Deheuvels, S.;
Elsworth, Y.; Jiménez-Reyes, S. J.; Michel, E.; Pérez Hernández,
F.; Roxburgh, I. W.; Salabert, D.
2009A&A...506...41G Altcode: 2009arXiv0907.0608G
Context: The F8 star HD 181906 (effective temperature ∼6300 K) was
observed for 156 days by the CoRoT satellite during the first long
run in the direction of the galactic centre. Analysis of the data
reveals a spectrum of solar-like acoustic oscillations. However, the
faintness of the target (m<SUB>v</SUB> = 7.65) means the signal-to-noise
(S/N) in the acoustic modes is quite low, and this low S/N leads to
complications in the analysis. <BR />Aims: We extract global variables
of the star, as well as key parameters of the p modes observed in the
power spectrum of the lightcurve. <BR />Methods: The power spectrum
of the lightcurve, a wavelet transform and spot fitting were used
to obtain the average rotation rate of the star and its inclination
angle. Then, the autocorrelation of the power spectrum and the power
spectrum of the power spectrum were used to properly determine the
large separation. Finally, estimations of the mode parameters were
done by maximizing the likelihood of a global fit, where several modes
were fit simultaneously. <BR />Results: We have been able to infer the
mean surface rotation rate of the star (~4 μHz) with indications of
the presence of surface differential rotation, the large separation
of the p modes (~87 μHz), hence also the “ridges” corresponding
to overtones of the acoustic modes. <P />CoRoT (Convection, Rotation
and planetary Transits) is a minisatellite developed by the French
Space agency CNES in collaboration with the Science Programmes of ESA,
Austria, Belgium, Brazil, Germany and Spain.
---------------------------------------------------------
Title: Transiting exoplanets from the CoRoT space
mission. VIII. CoRoT-7b: the first super-Earth with measured radius
Authors: Léger, A.; Rouan, D.; Schneider, J.; Barge, P.; Fridlund,
M.; Samuel, B.; Ollivier, M.; Guenther, E.; Deleuil, M.; Deeg, H. J.;
Auvergne, M.; Alonso, R.; Aigrain, S.; Alapini, A.; Almenara, J. M.;
Baglin, A.; Barbieri, M.; Bruntt, H.; Bordé, P.; Bouchy, F.; Cabrera,
J.; Catala, C.; Carone, L.; Carpano, S.; Csizmadia, Sz.; Dvorak,
R.; Erikson, A.; Ferraz-Mello, S.; Foing, B.; Fressin, F.; Gandolfi,
D.; Gillon, M.; Gondoin, Ph.; Grasset, O.; Guillot, T.; Hatzes, A.;
Hébrard, G.; Jorda, L.; Lammer, H.; Llebaria, A.; Loeillet, B.;
Mayor, M.; Mazeh, T.; Moutou, C.; Pätzold, M.; Pont, F.; Queloz, D.;
Rauer, H.; Renner, S.; Samadi, R.; Shporer, A.; Sotin, Ch.; Tingley,
B.; Wuchterl, G.; Adda, M.; Agogu, P.; Appourchaux, T.; Ballans, H.;
Baron, P.; Beaufort, T.; Bellenger, R.; Berlin, R.; Bernardi, P.;
Blouin, D.; Baudin, F.; Bodin, P.; Boisnard, L.; Boit, L.; Bonneau,
F.; Borzeix, S.; Briet, R.; Buey, J. -T.; Butler, B.; Cailleau, D.;
Cautain, R.; Chabaud, P. -Y.; Chaintreuil, S.; Chiavassa, F.; Costes,
V.; Cuna Parrho, V.; de Oliveira Fialho, F.; Decaudin, M.; Defise,
J. -M.; Djalal, S.; Epstein, G.; Exil, G. -E.; Fauré, C.; Fenouillet,
T.; Gaboriaud, A.; Gallic, A.; Gamet, P.; Gavalda, P.; Grolleau, E.;
Gruneisen, R.; Gueguen, L.; Guis, V.; Guivarc'h, V.; Guterman, P.;
Hallouard, D.; Hasiba, J.; Heuripeau, F.; Huntzinger, G.; Hustaix,
H.; Imad, C.; Imbert, C.; Johlander, B.; Jouret, M.; Journoud, P.;
Karioty, F.; Kerjean, L.; Lafaille, V.; Lafond, L.; Lam-Trong, T.;
Landiech, P.; Lapeyrere, V.; Larqué, T.; Laudet, P.; Lautier, N.;
Lecann, H.; Lefevre, L.; Leruyet, B.; Levacher, P.; Magnan, A.; Mazy,
E.; Mertens, F.; Mesnager, J. -M.; Meunier, J. -C.; Michel, J. -P.;
Monjoin, W.; Naudet, D.; Nguyen-Kim, K.; Orcesi, J. -L.; Ottacher,
H.; Perez, R.; Peter, G.; Plasson, P.; Plesseria, J. -Y.; Pontet, B.;
Pradines, A.; Quentin, C.; Reynaud, J. -L.; Rolland, G.; Rollenhagen,
F.; Romagnan, R.; Russ, N.; Schmidt, R.; Schwartz, N.; Sebbag, I.;
Sedes, G.; Smit, H.; Steller, M. B.; Sunter, W.; Surace, C.; Tello,
M.; Tiphène, D.; Toulouse, P.; Ulmer, B.; Vandermarcq, O.; Vergnault,
E.; Vuillemin, A.; Zanatta, P.
2009A&A...506..287L Altcode: 2009arXiv0908.0241L
Aims: We report the discovery of very shallow (Δ F/F ≈ 3.4×
10<SUP>-4</SUP>), periodic dips in the light curve of an active V =
11.7 G9V star observed by the CoRoT satellite, which we interpret as
caused by a transiting companion. We describe the 3-colour CoRoT
data and complementary ground-based observations that support
the planetary nature of the companion. <BR />Methods: We used
CoRoT colours information, good angular resolution ground-based
photometric observations in- and out- of transit, adaptive optics
imaging, near-infrared spectroscopy, and preliminary results from
radial velocity measurements, to test the diluted eclipsing binary
scenarios. The parameters of the host star were derived from optical
spectra, which were then combined with the CoRoT light curve to derive
parameters of the companion. <BR />Results: We examined all conceivable
cases of false positives carefully, and all the tests support the
planetary hypothesis. Blends with separation >0.40´´or triple
systems are almost excluded with a 8 × 10<SUP>-4</SUP> risk left. We
conclude that, inasmuch we have been exhaustive, we have discovered
a planetary companion, named CoRoT-7b, for which we derive a period
of 0.853 59 ± 3 × 10<SUP>-5</SUP> day and a radius of R<SUB>p</SUB>
= 1.68 ± 0.09 R_Earth. Analysis of preliminary radial velocity data
yields an upper limit of 21 M_Earth for the companion mass, supporting
the finding. <BR />Conclusions: CoRoT-7b is very likely the first
Super-Earth with a measured radius. This object illustrates what will
probably become a common situation with missions such as Kepler, namely
the need to establish the planetary origin of transits in the absence of
a firm radial velocity detection and mass measurement. The composition
of CoRoT-7b remains loosely constrained without a precise mass. A very
high surface temperature on its irradiated face, ≈1800-2600 K at the
substellar point, and a very low one, ≈50 K, on its dark face assuming
no atmosphere, have been derived. <P />The CoRoT space mission,
launched on 27 December 2006, has been developed and is operated by
CNES, with the contribution of Austria, Belgium, Brazil, ESA, Germany,
and Spain. First CoRoT data are available to the public from the
CoRoT archive: http://idoc-corot.ias.u-psud.fr. The complementary
observations were obtained with MegaPrime/MegaCam, a joint project of
CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which
is operated by NRC in Canada, INSU-CNRS in France, and the University of
Hawaii; ESO Telescopes at the La Silla and Paranal Observatories under
programme ID 081.C-0413(C), DDT 282.C-5015; the IAC80 telescope operated
by the Instituto de Astrofísica de Tenerife at the Observatorio del
Teide; the Isaac Newton Telescope (INT), operated on the island of
La Palma by the Isaac Newton group in the Spanish Observatorio del
Roque de Los Muchachos of the Instituto de Astrofisica de Canarias;
and at the Anglo-Australian Telescope that have been funded by the
Optical Infrared Coordination network (OPTICON), a major international
collaboration supported by the Research Infrastructures Programme of
the European Commissions Sixth Framework Programme; Radial-velocity
observations were obtained with the SOPHIE spectrograph at the 1.93m
telescope of Observatoire de Haute Provence, France.
---------------------------------------------------------
Title: A Doppler Spectro-Imager dedicated to Jovian seismology and
aeronomy onboard on Laplace/EJSM Jupiter Ganymede Orbiter
Authors: Schmider, F. X.; Gaulme, P.; Appourchaux, T.; Guillot, T.;
Mosser, B.; Rouesnel, F.; Sanchez-Lavega, A.; Tosi, F.; Mousis, O.;
Eff-Darwich, A.
2009epsc.conf...82S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Radius Determination of Solar-type Stars Using
Asteroseismology: What to Expect from the Kepler Mission
Authors: Stello, Dennis; Chaplin, William J.; Bruntt, Hans; Creevey,
Orlagh L.; García-Hernández, Antonio; Monteiro, Mario J. P. F. G.;
Moya, Andrés; Quirion, Pierre-Olivier; Sousa, Sergio G.; Suárez,
Juan-Carlos; Appourchaux, Thierry; Arentoft, Torben; Ballot, Jerome;
Bedding, Timothy R.; Christensen-Dalsgaard, Jørgen; Elsworth,
Yvonne; Fletcher, Stephen T.; García, Rafael A.; Houdek, Günter;
Jiménez-Reyes, Sebastian J.; Kjeldsen, Hans; New, Roger; Régulo,
Clara; Salabert, David; Toutain, Thierry
2009ApJ...700.1589S Altcode: 2009arXiv0906.0766S
For distant stars, as observed by the NASA Kepler satellite,
parallax information is currently of fairly low quality and is not
complete. This limits the precision with which the absolute sizes of
the stars and their potential transiting planets can be determined by
traditional methods. Asteroseismology will be used to aid the radius
determination of stars observed during NASA's Kepler mission. We
report on the recent asteroFLAG hare-and-hounds Exercise#2, where
a group of "hares" simulated data of F-K main-sequence stars that a
group of "hounds" sought to analyze, aimed at determining the stellar
radii. We investigated stars in the range 9 < V < 15, both
with and without parallaxes. We further test different uncertainties
in T <SUB>eff</SUB>, and compare results with and without using
asteroseismic constraints. Based on the asteroseismic large frequency
spacing, obtained from simulations of 4 yr time series data from
the Kepler mission, we demonstrate that the stellar radii can be
correctly and precisely determined, when combined with traditional
stellar parameters from the Kepler Input Catalogue. The radii found
by the various methods used by each independent hound generally agree
with the true values of the artificial stars to within 3%, when the
large frequency spacing is used. This is 5-10 times better than the
results where seismology is not applied. These results give strong
confidence that radius estimation can be performed to better than 3%
for solar-like stars using automatic pipeline reduction. Even when the
stellar distance and luminosity are unknown we can obtain the same level
of agreement. Given the uncertainties used for this exercise we find
that the input log g and parallax do not help to constrain the radius,
and that T <SUB>eff</SUB> and metallicity are the only parameters we
need in addition to the large frequency spacing. It is the uncertainty
in the metallicity that dominates the uncertainty in the radius.
---------------------------------------------------------
Title: SIAMOIS: asteroseismology in Antarctica
Authors: Mosser, B.; Buey, T.; Catala, C.; Appourchaux, T.; Charpinet,
S.; Mathias, Ph.; Maillard, J. P.; Siamois Team
2009CoAst.158..337M Altcode:
SIAMOIS is a ground-based asteroseismology project, to pursue velocity
measurements from the Dome C Concordia station in Antarctica. The
scientific program of SIAMOIS is based on the very precise asteroseismic
observation of nearby bright targets, focussing on the observations of
solar-like oscillations in solar-like stars. Spectrometric observations
with SIAMOIS will be able to detect l=3 oscillation modes that cannot
be analyzed with space-borne photometric observations. The Doppler
data, less affected by the stellar activity noise, will yield a more
precise mode structure inversion, thus a high-precision determination
of the stellar interior structure. The benefit of precise Doppler
observations of nearby targets, with addition of interferometric and
high-resolution spectrometric measurements, will allow us to investigate
in detail the physical laws governing the stellar interior structure and
evolution. <P />Dome C appears to be the ideal place for ground-based
asteroseismic observations as it is capable of delivering a duty
cycle as high as 90% during the three-month long polar night. This
duty cycle, a crucial point for asteroseismology, is comparable to
space-borne observations. The SIAMOIS concept is based on Fourier
Transform interferometry, which leads to a small instrument designed
and developed for the harsh conditions in Antarctica. The instrument
will be fully automatic, with no moving parts, and it will require
only a very simple initial set up in Antarctica.
---------------------------------------------------------
Title: Solar-Like Oscillations in a Massive Star
Authors: Belkacem, Kévin; Samadi, Réza; Goupil, Marie-Jo; Lefèvre,
Laure; Baudin, Fréderic; Deheuvels, Sébastien; Dupret, Marc-Antoine;
Appourchaux, Thierry; Scuflaire, Richard; Auvergne, Michel; Catala,
Claude; Michel, Eric; Miglio, Andrea; Montalban, Josefina; Thoul,
Anne; Talon, Suzanne; Baglin, Annie; Noels, Arlette
2009Sci...324.1540B Altcode: 2009arXiv0906.3788B
Seismology of stars provides insight into the physical mechanisms
taking place in their interior, with modes of oscillation probing
different layers. Low-amplitude acoustic oscillations excited by
turbulent convection were detected four decades ago in the Sun and
more recently in low-mass main-sequence stars. Using data gathered
by the Convection Rotation and Planetary Transits mission, we report
here on the detection of solar-like oscillations in a massive star,
V1449 Aql, which is a known large-amplitude (β Cephei) pulsator.
---------------------------------------------------------
Title: Measurement of Low Signal-To-Noise Ratio Solar p-Modes in
Spatially Resolved Helioseismic Data
Authors: Salabert, D.; Leibacher, J.; Appourchaux, T.; Hill, F.
2009ApJ...696..653S Altcode: 2009arXiv0902.2561S
We present an adaptation of the rotation-corrected, m-averaged
spectrum technique designed to observe low signal-to-noise ratio
(S/N), low-frequency solar p-modes. The frequency shift of each
of the 2l + 1 m spectra of a given (n, l) multiplet is chosen that
maximizes the likelihood of the m-averaged spectrum. A high S/N can
result from combining individual low S/N, individual-m spectra, none
of which would yield a strong enough peak to measure. We apply the
technique to Global Oscillation Network Group and Michelson Doppler
Imager data and show that it allows us to measure modes with lower
frequencies than those obtained with classic peak-fitting analysis
of the individual-m spectra. We measure their central frequencies,
splittings, asymmetries, lifetimes, and amplitudes. The low frequency,
low- and intermediate-angular degrees rendered accessible by this
new method correspond to modes that are sensitive to the deep solar
interior down to the core (l <= 3) and to the radiative interior
(4 <= l <= 35). Moreover, the low-frequency modes have deeper
upper turning points, and are thus less sensitive to the turbulence and
magnetic fields of the outer layers, as well as uncertainties in the
nature of the external boundary condition. As a result of their longer
lifetimes (narrower linewidths) at the same S/N the determination of
the frequencies of lower frequency modes is more accurate, and the
resulting inversions should be more precise.
---------------------------------------------------------
Title: Intrinsic photometric characterisation of stellar oscillations
and granulation. Solar reference values and CoRoT response functions
Authors: Michel, E.; Samadi, R.; Baudin, F.; Barban, C.; Appourchaux,
T.; Auvergne, M.
2009A&A...495..979M Altcode: 2008arXiv0809.1078M
Context: Measuring amplitudes of solar-like oscillations and the
granulation power spectral density constitute two promising sources
of information to improve our understanding and description of the
convection in outer layers of stars. However, different instruments,
using different techniques and different bandpasses, give measurements
that cannot be directly compared to each other or to theoretical
values. <BR />Aims: In this work, we define simple response functions to
derive intrinsic oscillation amplitudes and granulation power densities,
from photometry measurements obtained with a specific instrument
on a specific star. <BR />Methods: We test this method on different
photometry data sets obtained on the Sun with two different instruments
in three different bandpasses. <BR />Results: We show that the results
are in good agreement and we establish reference intrinsic values for
the Sun with photometry. We also compute the response functions of
the CoRoT instrument for a range of parameters representative of the
Main Sequence solar-like pulsators to be observed with CoRoT. We show
that these response functions can be conveniently described by simple
analytic functions of the effective temperature of the target star.
---------------------------------------------------------
Title: POLAR investigation of the Sun—POLARIS
Authors: Appourchaux, T.; Liewer, P.; Watt, M.; Alexander, D.;
Andretta, V.; Auchère, F.; D'Arrigo, P.; Ayon, J.; Corbard, T.;
Fineschi, S.; Finsterle, W.; Floyd, L.; Garbe, G.; Gizon, L.; Hassler,
D.; Harra, L.; Kosovichev, A.; Leibacher, J.; Leipold, M.; Murphy,
N.; Maksimovic, M.; Martinez-Pillet, V.; Matthews, B. S. A.; Mewaldt,
R.; Moses, D.; Newmark, J.; Régnier, S.; Schmutz, W.; Socker, D.;
Spadaro, D.; Stuttard, M.; Trosseille, C.; Ulrich, R.; Velli, M.;
Vourlidas, A.; Wimmer-Schweingruber, C. R.; Zurbuchen, T.
2009ExA....23.1079A Altcode: 2008ExA...tmp...40A; 2008arXiv0805.4389A
The POLAR Investigation of the Sun (POLARIS) mission uses a combination
of a gravity assist and solar sail propulsion to place a spacecraft
in a 0.48 AU circular orbit around the Sun with an inclination of 75°
with respect to solar equator. This challenging orbit is made possible
by the challenging development of solar sail propulsion. This first
extended view of the high-latitude regions of the Sun will enable
crucial observations not possible from the ecliptic viewpoint or from
Solar Orbiter. While Solar Orbiter would give the first glimpse of
the high latitude magnetic field and flows to probe the solar dynamo,
it does not have sufficient viewing of the polar regions to achieve
POLARIS’s primary objective: determining the relation between the
magnetism and dynamics of the Sun’s polar regions and the solar cycle.
---------------------------------------------------------
Title: Astrodynamical Space Test of Relativity Using Optical Devices
I (ASTROD I)—A class-M fundamental physics mission proposal for
Cosmic Vision 2015-2025
Authors: Appourchaux, Thierry; Burston, Raymond; Chen, Yanbei; Cruise,
Michael; Dittus, Hansjörg; Foulon, Bernard; Gill, Patrick; Gizon,
Laurent; Klein, Hugh; Klioner, Sergei; Kopeikin, Sergei; Krüger, Hans;
Lämmerzahl, Claus; Lobo, Alberto; Luo, Xinlian; Margolis, Helen; Ni,
Wei-Tou; Patón, Antonio Pulido; Peng, Qiuhe; Peters, Achim; Rasel,
Ernst; Rüdiger, Albrecht; Samain, Étienne; Selig, Hanns; Shaul,
Diana; Sumner, Timothy; Theil, Stephan; Touboul, Pierre; Turyshev,
Slava; Wang, Haitao; Wang, Li; Wen, Linqing; Wicht, Andreas; Wu, Ji;
Zhang, Xiaomin; Zhao, Cheng
2009ExA....23..491A Altcode: 2008arXiv0802.0582A
ASTROD I is a planned interplanetary space mission with multiple
goals. The primary aims are: to test general relativity with
an improvement in sensitivity of over three orders of magnitude,
improving our understanding of gravity and aiding the development of
a new quantum gravity theory; to measure key solar system parameters
with increased accuracy, advancing solar physics and our knowledge
of the solar system; and to measure the time rate of change of the
gravitational constant with an order of magnitude improvement and
the anomalous Pioneer acceleration, thereby probing dark matter and
dark energy gravitationally. It is an international project, with
major contributions from Europe and China and is envisaged as the
first in a series of ASTROD missions. ASTROD I will consist of one
spacecraft carrying a telescope, four lasers, two event timers and a
clock. Two-way, two-wavelength laser pulse ranging will be used between
the spacecraft in a solar orbit and deep space laser stations on Earth,
to achieve the ASTROD I goals. A second mission, ASTROD (ASTROD II)
is envisaged as a three-spacecraft mission which would test General
Relativity to 1 ppb, enable detection of solar g-modes, measure the
solar Lense-Thirring effect to 10 ppm, and probe gravitational waves
at frequencies below the LISA bandwidth. In the third phase (ASTROD
III or Super-ASTROD), larger orbits could be implemented to map the
outer solar system and to probe primordial gravitational-waves at
frequencies below the ASTROD II bandwidth.
---------------------------------------------------------
Title: First asteroseismic results from CoRoT
Authors: Michel, E.; Baglin, A.; Weiss, W. W.; Auvergne, M.; Catala,
C.; Aerts, C.; Appourchaux, T.; Barban, C.; Baudin, F.; Briquet,
M. -L.; Carrier, F.; Debosher, J.; De Ridder, J.; Garcia, R. A.;
Garrido, R.; Gutierrez, J.; Kallinger, T.; Lefevre, L.; Neiner, C.;
Poretti, E.; Samadi, R.; Sarro, L.; COROT Team
2008CoAst.157...69M Altcode:
About one year after the end of the first observational run and
six months after the first CoRoT data delivery, we comment the data
exploitation progress for different types of stars. We consider first
results to illustrate how these data of unprecedented quality shed a
new light on the field of stellar seismology.
---------------------------------------------------------
Title: Solar-like stars as seen by CoRoT
Authors: Garcia, R. A.; Appourchaux, T.; Baglin, A.; Auvergne, M.;
Barban, C.; Baudin, F.; Michel, E.; Mosser, B.; Samadi, R.; Data
Analysis Team D. A. T
2008CoAst.157..288G Altcode:
For more than a year, photometric high-quality data have been achieved
from the CoRoT (COnvection ROtation and Planetary Transits; Baglin et
al. 2006, Michel et al. 2008) min- isatellite developed by the French
space agency (CNES) in collaboration with the Science Program of ESA,
Austria, Belgium, Brazil Germany and Spain. The power spectrum of
4 dif- ferent solar-like stars (stars having sub-surface convective
zones showing an acoustic (p) mode spectrum) has been obtained with
unprecedented quality allowing the precise study of their seismic
properties. These solar-like stars are F stars with masses in the
range 1.0 to 1.4 M⊙ and are significantly hotter than the Sun.
---------------------------------------------------------
Title: First asteroseismic results from CoRoT
Authors: Michel, E.; Baglin, A.; Weiss, W. W.; Auvergne, M.; Catala,
C.; Aerts, C.; Appourchaux, T.; Barban, C.; Baudin, F.; Briquet, M.;
Carrier, F.; Degroote, P.; De Ridder, J.; Garcia, R. A.; Garrido,
R.; Gutiérrez-Soto, J.; Kallinger, T.; Lefevre, L.; Neiner,
C.; Poretti, E.; Samadi, R.; Sarro, L.; Alecian, G.; Andrade, L.;
Ballot, J.; Benomar, O.; Berthomieu, G.; Boumier, P.; Charpinet, S.;
de Batz, B.; Deheuvels, S.; Dupret, M. -A.; Emilio, M.; Fabregat,
J.; Facanha, W.; Floquet, M.; Frémat, Y.; Fridlund, M.; Goupil,
M. -J.; Grotsch-Noels, A.; Handler, G.; Huat, A. -L.; Hubert, A. -M.;
Janot-Pacheco, E.; Kjeldsen, H.; Lebreton, Y.; Leroy, B.; Martayan,
C.; Mathias, P.; Miglio, A.; Montalban, J.; Monteiro, M. J. P. F. G.;
Mosser, B.; Provost, J; Regulo, C.; Renan de Medeiros, J.; Ribas,
I.; Roca Cortés, T.; Roxburgh, I.; Suso, J.; Thoul, A.; Toutain, T.;
Tiphene, D.; Turck-Chieze, S.; Vauclair, S.; Vauclair, G.; Zwintz, K.
2008CoAst.156...73M Altcode:
About one year after the end of the first observational run and
six months after the first CoRoT data delivery, we comment the data
exploitation progress for different types of stars. We consider first
results to illustrate how these data of unprecedented quality shed a
new light on the field of stellar seismology.
---------------------------------------------------------
Title: A Multisite Campaign to Measure Solar-like Oscillations in
Procyon. I. Observations, Data Reduction, and Slow Variations
Authors: Arentoft, Torben; Kjeldsen, Hans; Bedding, Timothy R.;
Bazot, Michaël; Christensen-Dalsgaard, Jørgen; Dall, Thomas H.;
Karoff, Christoffer; Carrier, Fabien; Eggenberger, Patrick; Sosnowska,
Danuta; Wittenmyer, Robert A.; Endl, Michael; Metcalfe, Travis S.;
Hekker, Saskia; Reffert, Sabine; Butler, R. Paul; Bruntt, Hans;
Kiss, László L.; O'Toole, Simon J.; Kambe, Eiji; Ando, Hiroyasu;
Izumiura, Hideyuki; Sato, Bun'ei; Hartmann, Michael; Hatzes, Artie;
Bouchy, Francois; Mosser, Benoit; Appourchaux, Thierry; Barban,
Caroline; Berthomieu, Gabrielle; Garcia, Rafael A.; Michel, Eric;
Provost, Janine; Turck-Chièze, Sylvaine; Martić, Milena; Lebrun,
Jean-Claude; Schmitt, Jerome; Bertaux, Jean-Loup; Bonanno, Alfio;
Benatti, Serena; Claudi, Riccardo U.; Cosentino, Rosario; Leccia,
Silvio; Frandsen, Søren; Brogaard, Karsten; Glowienka, Lars; Grundahl,
Frank; Stempels, Eric
2008ApJ...687.1180A Altcode: 2008arXiv0807.3794A
We have carried out a multisite campaign to measure oscillations in
the F5 star Procyon A. We obtained high-precision velocity observations
over more than three weeks with 11 telescopes, with almost continuous
coverage for the central 10 days. This represents the most extensive
campaign so far organized on any solar-type oscillator. We describe in
detail the methods we used for processing and combining the data. These
involved calculating weights for the velocity time series from the
measurement uncertainties and adjusting them in order to minimize the
noise level of the combined data. The time series of velocities for
Procyon shows the clear signature of oscillations, with a plateau of
excess power that is centered at 0.9 mHz and is broader than has been
seen for other stars. The mean amplitude of the radial modes is 38.1
+/- 1.3 cm s<SUP>-1</SUP> (2.0 times solar), which is consistent with
previous detections from the ground and by the WIRE spacecraft, and
also with the upper limit set by the MOST spacecraft. The variation
of the amplitude during the observing campaign allows us to estimate
the mode lifetime to be 1.5<SUP>+ 1.9</SUP><SUB>-0.8</SUB> days. We
also find a slow variation in the radial velocity of Procyon, with good
agreement between different telescopes. These variations are remarkably
similar to those seen in the Sun, and we interpret them as being due to
rotational modulation from active regions on the stellar surface. The
variations appear to have a period of about 10 days, which presumably
equals the stellar rotation period or, perhaps, half of it. The amount
of power in these slow variations indicates that the fractional area of
Procyon covered by active regions is slightly higher than for the Sun.
---------------------------------------------------------
Title: SIAMOIS: Seismic Interferometer to Measure Oscillations in
the Interior of Stars
Authors: Mosser, Benoit; Appourchaux, Thierry; Catala, Claude; Buey,
Jean-Tristan; SIAMOIS Team
2008JPhCS.118a2042M Altcode:
SIAMOIS is a project devoted to ground-based asteroseismology,
involving an instrument to be installed at the Dome C Concordia station
in Antarctica. SIAMOIS provides an asteroseismic programme that can
follow the way currently opened by the space project CoRoT, with unique
information on G and K type bright stars on the main sequence. In
addition, spectrometric observations with SIAMOIS will be able to
detect oscillation modes that cannot be analyzed in photometry:
the Doppler data, less affected by the stellar activity noise,
yield a more precise mode structure inversion. The SIAMOIS concept
is based on Fourier Transform interferometry. Such a principle leads
to a small instrument designed and developed for the harsh conditions
in Antarctic. The instrument will be fully automatic, with no moving
parts, and a very simple initial set up in Antarctic. The dedicated
scientific programme will avoid the complications related to a
versatile instrument. Data reduction will be performed in real time,
and the transfer of the asteroseismic data to Europe will require
only a modest bandwidth. SIAMOIS will observe with a dedicated small
40-cm telescope. Dome C appears to be the ideal place for ground-based
asteroseismic observations. The unequalled weather conditions yield a
duty cycle as high as 90% over 3 months, as was observed during the 2005
wintering. This high duty cycle, a crucial point for asteroseismology,
is comparable to the best space-based observations. Long time series
(up to 3 months) will be possible, thanks to the long duration of the
polar night. SIAMOIS can be seen as one of the very first observational
projects in astronomy at Dome C. Its scientific programme will take
full advantage of the unique quality of this site, and will constitute a
necessary first step in preparation of future more ambitious programmes
requiring more sophisticated instrumentation and larger collectors.
---------------------------------------------------------
Title: Oscillations in Procyon A: First results from a multi-site
campaign
Authors: Hekker, S.; Arentoft, T.; Kjeldsen, H.; Bedding, T. R.;
Christensen-Dalsgaard, J.; Reffert, S.; Bruntt, H.; Butler, R. P.;
Kiss, L. L.; O'Toole, S. J.; Kambe, E.; Ando, H.; Izumiura, H.;
Sato, B.; Hartmann, M.; Hatzes, A. P.; Appourchaux, T.; Barban, C.;
Berthomieu, G.; Bouchy, F.; García, R. A.; Lebrun, J. -C.; Martić,
M.; Michel, E.; Mosser, B.; Nghiem, P. A. P.; Provost, J.; Samadi,
R.; Thévenin, F.; Turck-Chièze, S.; Bonanno, S. A.; Benatti, S.;
Claudi, R. U.; Cosentino, R.; Leccia, S.; Frandsen, S.; Brogaard,
K.; Grundahl, F.; Stempels, H. C.; Bazot, M.; Dall, T. H.; Karoff,
C.; Carrier, F.; Eggenberger, P.; Sosnowska, D.; Wittenmyer, R. A.;
Endl, M.; Metcalfe, T. S.
2008JPhCS.118a2059H Altcode: 2007arXiv0710.3772H
Procyon A is a bright F5IV star in a binary system. Although the
distance, mass and angular diameter of this star are all known with high
precision, the exact evolutionary state is still unclear. Evolutionary
tracks with different ages and different mass fractions of hydrogen
in the core pass, within the errors, through the observed position of
Procyon A in the Hertzsprung-Russell diagram. For more than15 years
several different groups have studied the solar-like oscillations in
Procyon A to determine its evolutionary state. Although several studies
independently detected power excess in the periodogram, there is no
agreement on the actual oscillation frequencies yet. This is probably
due to either insufficient high-quality data (i.e., aliasing) or due
to intrinsic properties of the star (i.e., short mode lifetimes). Now
a spectroscopic multi-site campaign using 10 telescopes world-wide
(minimizing aliasing effects) with a total time span of nearly 4
weeks (increase the frequency resolution) is performed to identify
frequencies in this star and finally determine its properties and
evolutionary state.
---------------------------------------------------------
Title: Detecting solar g modes with ASTROD
Authors: Burston, R.; Gizon, L.; Appourchaux, T.; Ni, W. -T.; ASTROD
I ESA cosmic vision 2015-2025 Team
2008JPhCS.118a2043B Altcode: 2008arXiv0802.1614B
We present an up-to-date estimate for the prospect of using the
Astrodynamical Space Test of Relativity using Optical Devices (ASTROD)
[1, 2, 3, 4] for an unambiguous detection of solar g modes (f < 400
μHz) through their gravitational signature. There are currently two
major efforts to detect low-frequency gravitational effects, ASTROD and
the Laser Interferometer Space Antenna (LISA) [5]. Using the most recent
g mode surface amplitude estimates, both observational and theoretical,
it is unclear whether LISA will be capable of successfully detecting
these modes. The ASTROD project may be better suited for detection as
its sensitivity curve is shifted towards lower frequencies with the
best sensitivity occurring in the range 100 - 300 μHz.
---------------------------------------------------------
Title: CoRoT Measures Solar-Like Oscillations and Granulation in
Stars Hotter Than the Sun
Authors: Michel, Eric; Baglin, Annie; Auvergne, Michel; Catala,
Claude; Samadi, Reza; Baudin, Frédéric; Appourchaux, Thierry; Barban,
Caroline; Weiss, Werner W.; Berthomieu, Gabrielle; Boumier, Patrick;
Dupret, Marc-Antoine; Garcia, Rafael A.; Fridlund, Malcolm; Garrido,
Rafael; Goupil, Marie-Jo; Kjeldsen, Hans; Lebreton, Yveline; Mosser,
Benoît; Grotsch-Noels, Arlette; Janot-Pacheco, Eduardo; Provost,
Janine; Roxburgh, Ian W.; Thoul, Anne; Toutain, Thierry; Tiphène,
Didier; Turck-Chieze, Sylvaine; Vauclair, Sylvie D.; Vauclair,
Gérard P.; Aerts, Conny; Alecian, Georges; Ballot, Jérôme;
Charpinet, Stéphane; Hubert, Anne-Marie; Lignières, François;
Mathias, Philippe; Monteiro, Mario J. P. F. G.; Neiner, Coralie;
Poretti, Ennio; Renan de Medeiros, José; Ribas, Ignasi; Rieutord,
Michel L.; Roca Cortés, Teodoro; Zwintz, Konstanze
2008Sci...322..558M Altcode: 2008arXiv0812.1267M
Oscillations of the Sun have been used to understand its interior
structure. The extension of similar studies to more distant stars
has raised many difficulties despite the strong efforts of the
international community over the past decades. The CoRoT (Convection
Rotation and Planetary Transits) satellite, launched in December 2006,
has now measured oscillations and the stellar granulation signature
in three main sequence stars that are noticeably hotter than the
sun. The oscillation amplitudes are about 1.5 times as large as
those in the Sun; the stellar granulation is up to three times as
high. The stellar amplitudes are about 25% below the theoretic values,
providing a measurement of the nonadiabaticity of the process ruling
the oscillations in the outer layers of the stars.
---------------------------------------------------------
Title: solarFLAG hare and hounds: estimation of p-mode frequencies
from Sun-as-star helioseismology data
Authors: Jiménez-Reyes, S. J.; Chaplin, W. J.; García, R. A.;
Appourchaux, T.; Baudin, F.; Boumier, P.; Elsworth, Y.; Fletcher,
S. T.; Lazrek, M.; Leibacher, J. W.; Lochard, J.; New, R.; Régulo,
C.; Salabert, D.; Toutain, T.; Verner, G. A.; Wachter, R.
2008MNRAS.389.1780J Altcode: 2008arXiv0807.0989J; 2008MNRAS.tmp..954J; 2008MNRAS.tmp.1026J
We report on the results of the latest solarFLAG hare-and-hounds
exercise, which was concerned with testing methods for extraction
of frequencies of low-degree solar p modes from data collected
by Sun-as-a-star observations. We have used the new solarFLAG
simulator, which includes the effects of correlated mode excitation and
correlations with background noise, to make artificial time-series data
that mimic Doppler velocity observations of the Sun-as-a-star. The
correlations give rise to asymmetry of mode peaks in the frequency
power spectrum. 10 members of the group (the hounds) applied their
`peak-bagging' codes to a 3456-d data set, and the estimated
mode frequencies were returned to the hare (who was WJC) for
comparison. Analysis of the results reveals a systematic bias in the
estimated frequencies of modes above ~1.8mHz. The bias is negative,
meaning the estimated frequencies systematically underestimate the
input frequencies. <P />We identify two sources that are the dominant
contributions to the frequency bias. Both sources involve failure to
model accurately subtle aspects of the observed power spectral density
in the part (window) of the frequency power spectrum that is being
fitted. One source of bias arises from a failure to account for the
power spectral density coming from all those modes whose frequencies lie
outside the fitting windows. The other source arises from a failure to
account for the power spectral density of the weak l = 4 and 5 modes,
which are often ignored in Sun-as-a-star analysis. The Sun-as-a-star
peak-bagging codes need to allow for both sources, otherwise the
frequencies are likely to be biased.
---------------------------------------------------------
Title: AsteroFLAG — from the Sun to the stars
Authors: Chaplin, W. J.; Appourchaux, T.; Arentoft, T.; Ballot, J.;
Baudin, F.; Bazot, M.; Bedding, T. R.; Christensen-Dalsgaard, J.;
Creevey, O. L.; Duez, V.; Elsworth, Y.; Fletcher, S. T.; García,
R. A.; Gough, D. O.; Jiménez, A.; Jiménez-Reyes, S. J.; Houdek, G.;
Kjeldsen, H.; Lazrek, M.; Leibacher, J. W.; Monteiro, M. J. P. F. G.;
Neiner, C.; New, R.; Régulo, C.; Salabert, D.; Samadi, R.; Sekii,
T.; Sousa, S. G.; Toutain, T.; Turck-Chièze, S.
2008JPhCS.118a2048C Altcode:
We stand on the threshold of a critical expansion of asteroseismology
of Sun-like stars, the study of stellar interiors by observation
and analysis of their global acoustic modes of oscillation. The
Sun-like oscillations give a very rich spectrum allowing the internal
structure and dynamics to be probed down into the stellar cores to
very high precision. Asteroseismic observations of many stars will
allow multiple-point tests of crucial aspects of stellar evolution
and dynamo theory. The aims of the asteroFLAG collaboration are to
help the community to refine existing, and to develop new, methods
for analysis of the asteroseismic data on the Sun-like oscillators.
---------------------------------------------------------
Title: Development of a new analysis technique to measure low
radial-order p modes in spatially-resolved helioseismic data
Authors: Salabert, David; Leibacher, John W.; Appourchaux, Thierry
2008JPhCS.118a2086S Altcode: 2007arXiv0711.2825S
In order to take full advantage of the long time series collected by
the GONG and MDI helioseismic projects, we present here an adaptation
of the rotation-corrected m-averaged spectrum technique in order to
observe low radial-order solar p modes. Modeled profiles of the solar
rotation demonstrated the potential advantage of such a technique
[1, 2, 3]. Here we develop a new analysis procedure which finds the
best estimates of the shift of each m of a given (n, ι) multiplet,
commonly expressed as an expansion in a set of orthogonal polynomials,
which yield the narrowest mode in the m-averaged spectrum. We apply the
technique to the GONG data for modes with 1 <= ι <= 25 and show
that it allows us to measure lower-frequency modes than with classic
peak-fitting analysis of the individual-m spectra.
---------------------------------------------------------
Title: CoRoT sounds the stars: p-mode parameters of Sun-like
oscillations on HD 49933
Authors: Appourchaux, T.; Michel, E.; Auvergne, M.; Baglin, A.;
Toutain, T.; Baudin, F.; Benomar, O.; Chaplin, W. J.; Deheuvels, S.;
Samadi, R.; Verner, G. A.; Boumier, P.; García, R. A.; Mosser, B.;
Hulot, J. -C.; Ballot, J.; Barban, C.; Elsworth, Y.; Jiménez-Reyes,
S. J.; Kjeldsen, H.; Régulo, C.; Roxburgh, I. W.
2008A&A...488..705A Altcode:
Context: The first asteroseismology results from CoRoT are presented,
on a star showing Sun-like oscillations. We have analyzed a 60 day
lightcurve of high-quality photometric data collected by CoRoT on the
F5 V star HD 49933. The data reveal a rich spectrum of overtones of
low-degree p modes. <BR />Aims: Our aim was to extract robust estimates
of the key parameters of the p modes observed in the power spectrum of
the lightcurve. <BR />Methods: Estimation of the mode parameters was
performed using maximum likelihood estimation of the power spectrum. A
global fitting strategy was adopted whereby 15 mode orders of the
mode spectrum (45 modes) were fitted simultaneously. <BR />Results:
The parameter estimates that we list include mode frequencies,
peak linewidths, mode amplitudes, and a mean rotational frequency
splitting. We find that the average large frequency (overtone) spacing
derived from the fitted mode frequencies is 85.9 ± 0.15 μHz. The
frequency of maximum amplitude of the radial modes is at 1760 μHz,
where the observed rms mode amplitude is 3.75 ± 0.23 ppm. The mean
rotational splitting of the non-radial modes appears to be in the
range ≈2.7 μHz to ≈3.4 μHz. The angle of inclination offered by
the star, as determined by fits to the amplitude ratios of the modes,
appears to be in the range ≈50 degrees to ≈62 degrees. <P />The
CoRoT space mission, launched on <P />2006 December 27, was developed
and is operated by the CNES, with <P />participation of the Science
Programs of ESA, ESA's RSSD, Austria, <P />Belgium, Brazil, Germany
and Spain.
---------------------------------------------------------
Title: On deriving p-mode parameters for inclined solar-like stars
Authors: Ballot, J.; Appourchaux, T.; Toutain, T.; Guittet, M.
2008A&A...486..867B Altcode: 2008arXiv0803.0885B
Context: Thanks to their high quality, new and upcoming asteroseismic
observations, with CoRoT, Kepler, and from the ground, benefit from
experience gained with helioseismology. <BR />Aims: We focus, in
this paper, on solar-like oscillations, for which the inclination of
the rotation axis is unknown. We present a theoretical study of the
errors of p-mode parameters determined by means of a maximum-likelihood
estimator, and we also analyze correlations and biases. <BR />Methods:
We used different, complementary approaches: we performed either
semi-analytical computation of the Hessian matrix, fitting of single
mean profiles, or Monte Carlo simulations. <BR />Results: First, we
give analytical approximations for the errors of frequency, inclination
and rotational splitting. The determination of the inclination is
very challenging for the common case of slow rotators (like the
Sun), making the determination of a reliable rotational splitting
difficult. Moreover, due to the numerous correlations, biases - more
or less significant - can appear in the determination of various
parameters in the case of bad inclination fittings, especially when
a locking at 90° occurs. We also discuss this issue. Nevertheless,
the central frequency and some derived parameters, such as the total
power of the mode, are free of such biases.
---------------------------------------------------------
Title: Challenges for asteroseismic analysis of Sun-like stars
Authors: Chaplin, W. J.; Houdek, G.; Appourchaux, T.; Elsworth, Y.;
New, R.; Toutain, T.
2008A&A...485..813C Altcode: 2008arXiv0804.4371C
Context: Asteroseismology of Sun-like stars is undergoing rapid
expansion with, for example, new data from the CoRoT mission and
continuation of ground-based campaigns. There is also the exciting
upcoming prospect of NASA's Kepler mission, which will allow the
asteroseismic study of several hundred Sun-like targets, in some cases
for periods lasting up to a few years. <BR />Aims: The seismic mode
parameters are the input data needed for making inference on stars
and their internal structures. In this paper we discuss the ease with
which it will be possible to extract estimates of individual mode
parameters, dependent on the mass, age, and visual brightness of the
star. Our results are generally applicable; however, we look at mode
detectability in the context of the upcoming Kepler observations. <BR
/>Methods: To inform our discussions we make predictions of various
seismic parameters. To do this we use simple empirical scaling relations
and detailed pulsation computations of the stochastic excitation and
damping characteristics of the Sun-like p modes. <BR />Results: The
issues related to parameter extraction on individual p modes discussed
here are mode detectability, the detectability and impact of stellar
activity cycles, and the ability to measure properties of rotationally
split components, which is dependent on the relative importance of
the rotational characteristics of the star and the damping of the
stochastically excited p modes.
---------------------------------------------------------
Title: Design of a Fabry-Perot interferometer for the SO/PHI
instrument on Solar Orbiter
Authors: Trosseille, Clément; Appourchaux, Thierry; Fourmond,
Jean-Jacques
2008SPIE.7010E..17T Altcode: 2008SPIE.7010E..37T
We present our work on the spectral analyser of the Polarimetric
and Helioseismic Imager (PHI) instrument to be flown aboard ESA's
Solar Orbiter mission. We detail the choices that were made to
determine the concept of the spectral analyser, a Lithium Niobate
Fabry-Perot interferometer, and its characteristics, as to fulfil both
scientific needs and technical requirements. We will present the first
experimental results - including stability, repeatability, parallelism,
spectral homogeneity and imaging capability - on an air-spaced
piezoelectric-tunable etalon, which is the backup solution for PHI.
---------------------------------------------------------
Title: Effect of the stellar inclination angle upon theoretical
errors of l=1 p-mode parameters
Authors: Ballot, J.; Appourchaux, T.; Toutain, T.
2008AN....329..558B Altcode:
The asteroseismic observations provided by current and future
missions like CoRoT or Kepler will have a quality closer to those
obtained for the Sun. In this context, tools and methods developed
for helioseismology can be applied to other stars. In this paper,
we focus on solar-like oscillations of stars with an unknown rotation
axis inclination and study, by means of maximum-likelihood estimation,
the errors on the determination of l=1 p-mode parameters.
---------------------------------------------------------
Title: AsteroFLAG: First results from hare-and-hounds Exercise #1
Authors: Chaplin, W. J.; Appourchaux, T.; Arentoft, T.; Ballot, J.;
Christensen-Dalsgaard, J.; Creevey, O. L.; Elsworth, Y.; Fletcher,
S. T.; García, R. A.; Houdek, G.; Jiménez-Reyes, S. J.; Kjeldsen,
H.; New, R.; Régulo, C.; Salabert, D.; Sekii, T.; Sousa, S. G.;
Toutain, T.; rest of asteroFLAG Group
2008AN....329..549C Altcode: 2008arXiv0803.4143C
We report on initial results from the first phase of Exercise #1 of the
asteroFLAG hare and hounds. The asteroFLAG group is helping to prepare
for the asteroseismology component of NASA's Kepler mission, and the
first phase of Exercise #1 is concerned with testing extraction of
estimates of the large and small frequency spacings of the low-degree p
modes from Kepler-like artificial data. These seismic frequency spacings
will provide key input for complementing the exoplanet search data.
---------------------------------------------------------
Title: Helioseismology program for the PICARD satellite
Authors: Corbard, T.; Boumier, P.; Appourchaux, T.; Jiménez-Reyes,
S. J.; Gelly, B.; PICARD Team
2008AN....329..508C Altcode:
The PICARD mission is a CNES micro-satellite to be launched in 2009. Its
goal is to better understand the Sun and the potential impact of
its activity on earth climate by measuring simultaneously the solar
total and spectral irradiance, diameter, shape and oscillations. We
present the scientific objectives, instrumental requirements and
data products of the helioseismology program of PICARD which aims
to observe the low to medium l p-mode oscillations in intensity
and search for g-mode oscillation signatures at the limb. <P
/>http://www.picard-mission.cnes.fr
---------------------------------------------------------
Title: Bayesian approach for g-mode detection, or how to restrict
our imagination
Authors: Appourchaux, T.
2008AN....329..485A Altcode: 2007arXiv0711.0435A
Nowadays, g-mode detection is based upon a priori theoretical
knowledge. By doing so, detection becomes more restricted to what we can
imagine. De facto, the universe of possibilities is made narrower. Such
an approach is pertinent for Bayesian statisticians. Examples of
how Bayesian inferences can be applied to spectral analysis and
helioseismic power spectra are given. Our intention is not to give
the full statistical framework (much too ambitious) but to provide
an appetizer for going further in the direction of a proper Bayesian
inference, especially for detecting gravity modes.
---------------------------------------------------------
Title: Low-Frequency Solar p Modes in GONG and MDI Observations
using m-Averaged Spectra
Authors: Leibacher, J.; Salabert, D.; Appourchaux, T.; Hill, F.
2008AGUSMSP41A..06L Altcode:
The GONG and MDI global helioseismology pipelines provide solar acoustic
mode parameters for 108- and 72-day time series respectively by fitting
the 2 ℓ + 1 individual-m spectra of a given (n, ℓ/) multiplet
either individually (GONG) or simultaneously (MDI). Our knowledge of
the variable solar interior through helioseismic observations derives
primarily from these two analysis pipelines. We have developed a
new method to extract the mode parameters by adjusting the rotation-
and structure-induced frequency shift for each m-spectrum to minimize
the mode width in the m-averaged spectrum. The m-averaged spectrum
appears to be a powerful tool for low signal-to-noise-ratio modes in the
low-frequency range where the modes have very long lifetimes. Indeed,
in the case of spatially-resolved helioseismic data (MDI, GONG, HMI),
for a given multiplet (n, ℓ/), there exist 2 ℓ + 1 individual-m
spectra, which can result in an average spectrum with a SNR ≫ 1 even
when the individual-m spectra have a SNR < 1. We show here that
the m-averaged spectrum technique, applied to the GONG 108-day and MDI
72-day time series, gives us access to a whole new range of predicted,
low-SNR modes that had not been successfully fitted by the current
MDI and GONG peak-fitting pipelines. We show that the modes that are
measured by both techniques are extracted without bias. We apply this
technique to 360-, 720-, 1080-, and 1440-day long GONG time series to
infer the variability of the mode parameters with solar activity in
the low-frequency range below ~ 1500 μHz.
---------------------------------------------------------
Title: Searching for p-modes in MOST Procyon data: another view
Authors: Baudin, F.; Appourchaux, T.; Boumier, P.; Kuschnig, R.;
Leibacher, J. W.; Matthews, J. M.
2008A&A...478..461B Altcode: 2007arXiv0711.0601B
Context: Photometry of Procyon obtained by the MOST satellite in
2004 has been searched for p modes by several groups, with sometimes
contradictory interpretations. <BR />Aims: We explore two possible
factors that complicate the analysis and may lead to erroneous reports
of p modes in these data. <BR />Methods: Two methods are used to
illustrate the role of subtle instrumental effects in the photometry:
time-frequency analysis, and a search for regularly spaced peaks in a
Fourier spectrum based on the echelle diagramme approach. <BR />Results:
We find no convincing evidence of a p-mode signal in the MOST Procyon
data. We can account for an apparent excess of power close to the p-mode
frequency range and signs of structure in an echelle diagramme in terms
of instrumental effects. <P />Based on data from the MOST satellite,
a Canadian Space Agency mission, jointly operated by Dynacon Inc., the
University of Toronto Institute for Aerospace Studies and the University
of British Columbia, with the assistance of the University of Vienna.
---------------------------------------------------------
Title: Asteroseismology of Procyon with SOPHIE
Authors: Mosser, B.; Bouchy, F.; Martić, M.; Appourchaux, T.; Barban,
C.; Berthomieu, G.; Garcia, R. A.; Lebrun, J. C.; Michel, E.; Provost,
J.; Thévenin, F.; Turck-Chièze, S.
2008A&A...478..197M Altcode: 2007arXiv0712.1368M
Context: This paper reports a 9-night asteroseismic observation
program conducted in January 2007 with the new spectrometer sophie
at the OHP 193-cm telescope, on the F5 IV-V target Procyon A. <BR
/>Aims: This first asteroseismic program with sophie was intended
to test the performance of the instrument with a bright but demanding
asteroseismic target and was part of a multisite network. <BR />Methods:
The sophie spectra have been reduced with the data reduction software
provided by OHP. The Procyon asteroseismic data were then analyzed
with statistical tools. The asymptotic analysis has been conducted
considering possible curvature in the échelle diagram analysis. <BR
/>Results: These observations have proven the efficient performance of
sophie used as an asteroseismometer, and succeed in a clear detection
of the large spacing. An échelle diagram based on the 54-μHz
spacing shows clear ridges. Identification of the peaks exhibits
large spacings varying from about 52 μHz to 56 μHz. Outside
the frequency range [0.9, 1.0 mHz] where the identification is
confused, the large spacing increases at a rate of about dΔν/dn
≃ 0.2 μHz. This may explain some of the different values of
the large spacing obtained by previous observations. <P />Based on
observations collected with the sophie échelle spectrometer mounted
on the 1.93-m telescope at OHP, France (program 06B.PNPS.BOU);
http://www.obs-hp.fr/www/guide/ sophie/sophie-eng.html Table of
radial velocity measurements is only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/478/197
---------------------------------------------------------
Title: VizieR Online Data Catalog: Procyon (alpha CMi) radial
velocities (Mosser+, 2008)
Authors: Mosser, B.; Bouchy, F.; Martic, M.; Appourchaux, T.; Barban,
C.; Berthomieu, G.; Garcia, R. A.; Lebrun, J. C.; Michel, E.; Provost,
J.; Thevenin, F.; Turck-Chieze, S.
2007yCat..34780197M Altcode:
Time series of the radial velocities of Procyon recorder with the
echelle spectrometer SOPHIE at Observatoire de Haute Provence in
January 2007. <P />(1 data file).
---------------------------------------------------------
Title: Simu-LC : a Light-Curve simulator for CoRoT
Authors: Baudin, F.; Samadi, R.; Appourchaux, T.; Michel, E.
2007arXiv0710.3378B Altcode:
Simulating the data that a space instrument like COROT will provide
might look presomptuous. Indeed, it is certainly, when comparing to
previous comparable instruments like IPHIR or GOLF. These two examples
show that the nominal behaviour of the instrument is not always
reached, but this does not prevent this instrument to provide very
interesting data. However, despite some technical problems, IPHIR and
GOLF yielded a wealth of scientific results. Thus, what is the interest
of simulating COROT data? How close to reality these simualtions will
get? This might not be the most important fact as the preparation of
these simulations will help us to prepare the analysis of real data and
to be ready in case of unexpected technical behaviour of the instrument
perturbating the data, or unexpected physical behaviour of the targets
of the instrument. A consequence of that is that the simulation tool
must include technical and physical aspects, making the task even more
difficult. These aspects cover: photon noise, p modes excitation,
granulation signal, stellar activity signal, orbital perturbations,
stellar rotation... The software presented here is freely available at:
http://www.lesia.obspm.fr/~corotswg/simulightcurve.html
---------------------------------------------------------
Title: Needles in haystacks: how to use contemporaneous data in the
search for low-frequency modes of oscillation of the Sun
Authors: Broomhall, A. M.; Chaplin, W. J.; Elsworth, Y.; Appourchaux,
T.
2007MNRAS.379....2B Altcode: 2007MNRAS.tmp..525B
We show how to take advantage of contemporaneous data from two different
instruments in the search for low-frequency modes of oscillation of
the Sun. Contemporaneous data allow searches to be made for prominent,
sharp concentrations of power which are coincident in frequency. Crucial
to determining objective measures of the joint probability of the
random occurrence of such features, which are potential candidates
for modes, is a good understanding of the characteristics of the
background noise. In this paper we show how to make proper allowance,
in the calculation of the probability, for noise that is common to data
from different instruments. This common noise is solar in origin, and
comes from the solar granulation. Its presence makes calculation of the
probability a non-trivial problem. We demonstrate application of the
technique in searches for low-frequency p modes. The data we searched
comprised 3071 d of contemporaneous Sun-as-a-star Doppler velocity
observations made by the ground-based Birmingham Solar-Oscillations
Network (BiSON), and the GOLF instrument onboard the ESA/NASA SOHO
spacecraft.
---------------------------------------------------------
Title: On understanding the meaning of l = 2 and 3 p-mode frequencies
as measured by various helioseismic instruments
Authors: Appourchaux, T.; Chaplin, W. J.
2007A&A...469.1151A Altcode:
Aims:Frequencies of the low-degree p-mode oscillations of the Sun
may be extracted either from data collected by instruments that make
full-disc observations of the Sun as a star, or from data collected
by instruments that resolve, or image, the Sun's surface onto many
detector elements. The two methods can show marked differences in
their sensitivity to modes having certain combinations of degree and
azimuthal order. These different sensitivities lead to differences
in measurements of the central frequencies of the modes, which must
be properly accounted for if data from two different instruments
are to be compared, or combined. <BR />Methods: We perform an
analytical derivation of the p-mode frequency offsets expected between
contemporaneous Sun-as-a-star and resolved-Sun data. <BR />Results:
Here, we demonstrate that the empirical factors derived by Chaplin et
al. (2004, A&A, 424, 713) are reproduced by our analysis, but with
a more marked dependence upon the mode linewidth.
---------------------------------------------------------
Title: Rotation Of The Deep Solar Interior From A Solar Cycle Of
Gong Data
Authors: Leibacher, John W.; Salabert, D.; Appourchaux, T.; Hill,
F.; Howe, R.
2007AAS...210.2219L Altcode: 2007BAAS...39..127L
We use 3960 days of Global Oscillation Network Group (GONG) data
to derive the rotation of the deep solar interior. We obtain the
splitting of low signal-to-noise multiplets - at low radial order
and low spherical harmonic degree - using the m-averaged spectra - a
technique that works well even when none of the individual-m spectra are
clean enough to be fit. Central frequencies and rotational splittings
are estimated down to l = 1 and 1 mHz. We illustrate here the validity
of our method and infer the radial rotation profile down to 0.2 solar
radius. <P />This work utilizes data obtained by the Global Oscillation
Network Group (GONG) program, managed by the National Solar Observatory,
which is operated by AURA, Inc. under a cooperative agreement with
the National Science Foundation. The data were acquired by instruments
operated by the Big Bear Solar Observatory, High Altitude Observatory,
Learmonth Solar Observatory, Udaipur Solar Observatory, Instituto de
Astrofisica de Canarias, and Cerro Tololo Interamerican Observatory.
---------------------------------------------------------
Title: On cross-spectrum capabilities for detecting stellar
oscillation modes
Authors: Appourchaux, T.; Leibacher, J.; Boumier, P.
2007A&A...463.1211A Altcode:
Aims:Long-lived stellar oscillation modes are usually detected using
Fourier transforms of time series of stellar radial velocities or
brightness. It is commonly thought that one could use the cross spectrum
of the two signals, or alternatively use the interleaved series of a
single signal, to considerably improve the detection level by reducing
the noise level. <BR />Methods: We use a statistical analysis of the
cross spectrum to compute its mean value and rms value, and use the
associated signal-to-noise ratio for stochastically excited modes. <BR
/>Results: Here, we demonstrate that the gain in the signal-to-noise
ratio can indeed be improved for modes with a shorter lifetime than
the observation time, but not those with a longer lifetime than the
observation time.
---------------------------------------------------------
Title: EUI, The Ultraviolet Imaging Telescopes Of Solar Orbiter
Authors: Hochedez, J. -F.; Appourchaux, T.; Defise, J. -M.; Harra,
L. K.; Schühle, U.; Auchère, F.; Curdt, W.; Hancock, B.; Kretzschmar,
M.; Lawrence, G.; Leclec'h, J. -C.; Marsch, E.; Mercier, R.; Parenti,
S.; Podladchikova, E.; Ravet, M. -F.; Rochus, P.; Rodriguez, L.;
Rouesnel, F.; Solanki, S.; Teriaca, L.; Van Driel, L.; Vial, J. -C.;
Winter, B.; Zhukov, A.
2007ESASP.641E..33H Altcode:
The scientific objectives of Solar Orbiter rely ubiquitously on EUI,
its suite of solar atmosphere imaging telescopes. In the configuration
discussed here, EUI includes three co-aligned High Resolution Imagers
(HRI) and one Full Sun Imager (FSI). FSI and two HRIs observe in extreme
ultraviolet passbands, dominated by coronal emission. Another HRI is
designed for the hydrogen Lyman α radiation in the far UV, imaging the
Chromosphere and the lower Transition Region. The current EUI design
and some of its development challenges are highlighted. EUI profits from
co-rotation phases, solar proximity and departure from the ecliptic. In
synergy with the other S.O. payload, EUI probes the dynamics of the
solar atmosphere, provides context data for all investigations and helps
to link in-situ and remote-sensing observations. In short, it serves all
four top-level goals of the mission. For these reasons, the EUI suite
is keenly anticipated in the European scientific community and beyond.
---------------------------------------------------------
Title: Design Of A Fabry Perot Interferometer For The VIM Instrument
Aboard Solar Orbiter
Authors: Trosseille, C.; Appourchaux, T.; Martinez Pillet, V.
2007ESASP.641E..85T Altcode:
The spectral analyser of the Visible light Imager and Magnetograph
(VIM) is a critical device whose concept is dependent on scientific
requirements and technical trade-offs, which are directly driven by
the nature of the mission. Here, we report on the choices that were
made to fulfill the scientific needs, while constantly keeping an eye
on feasibility. We also list the critical points and remaining issues
that should be investigated and addressed properly in further work.
---------------------------------------------------------
Title: Evaluation of the Scientific Performances for the Seismology
Programme
Authors: Appourchaux, T.; Berthomieu, G.; Michel, E.; Ballot, J.;
Barban, C.; Baudin, F.; Boumier, P.; De Ridder, J.; Floquet, M.;
Garcia, R. A.; Garrido, R.; Goupil, M. -J.; Lambert, P.; Lochard,
J.; Mazumdar, A.; Neiner, C.; Poretti, E.; Provost, J.; Roxburgh,
I.; Samadi, R.; Toutain, T.
2006ESASP1306..429A Altcode:
The Data Analysis Team of the Seismology Working Group of COROT
performed several hare-and-hound exercises. These exercises aimed at
putting the team in a situation as if they would analyze data coming
out of the COROT spacecraft. In total the team performed five different
exercises simulating solar-like stars (HH#1, HH#2, HH#3), classical
pulsators (HH#5), validating seismic calibration of stellar model (HH#2,
HH#3) and pushing the limit of detection (HH#4). This paper tries both
to serve as a summary and as a portal to other publications of the DAT.
---------------------------------------------------------
Title: Data Analysis Tools for the Seismology Programme
Authors: Appourchaux, T.; Berthomieu, G.; Michel, E.; Aerts, C.;
Ballot, J.; Barban, C.; Baudin, F.; Boumier, P.; De Ridder, J.;
Floquet, M.; Garcia, R. A.; Garrido, R.; Goupil, M. -J.; Lambert,
P.; Lochard, J.; Neiner, C.; Poretti, E.; Provost, J.; Roxburgh, I.;
Samadi, R.; Toutain, T.
2006ESASP1306..377A Altcode:
Tools developed by helioseismologists and by classical-pulsator
astronomers have been used in the hare-and-hound exercises for having
a several different ways of deriving the oscillation mode parameters
such as frequency or amplitude. These tools are used for deriving what
we call recipes that will allow us to obtain the mode parameters from
light curves either for solar-like stars or for classical pulsators. The
recipes are used for tagging the mode parameters as being those of
COROT. They will be used as reference or yardstick for other fitting
strategies. We will also address the issue of mode detection. Additional
tools such as time-frequency analysis will be presented.
---------------------------------------------------------
Title: The Research and Scientific Support Department of ESA and CoRoT
Authors: Fridlund, M.; Beaufort, T.; Favata, F.; Foing, B.; Gimenéz,
A.; Gondoin, P.; Johlander, B.; Smit, H.; Sunter, W.; Appourchaux, T.
2006ESASP1306..133F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Seismology Programme of CoRoT
Authors: Michel, E.; Baglin, A.; Auvergne, M.; Catala, C.; Aerts,
C.; Alecian, G.; Amado, P.; Appourchaux, T.; Ausseloos, M.; Ballot,
J.; Barban, C.; Baudin, F.; Berthomieu, G.; Boumier, P.; Bohm, T.;
Briquet, M.; Charpinet, S.; Cunha, M. S.; De Cat, P.; Dupret, M. A.;
Fabregat, J.; Floquet, M.; Fremat, Y.; Garrido, R.; Garcia, R. A.;
Goupil, M. -J.; Handler, G.; Hubert, A. -M.; Janot-Pacheco, E.;
Lambert, P.; Lebreton, Y.; Lignieres, F.; Lochard, J.; Martin-Ruiz,
S.; Mathias, P.; Mazumdar, A.; Mittermayer, P.; Montalban, J.;
Monteiro, M. J. P. F. G.; Morel, P.; Mosser, B.; Moya, A.; Neiner,
C.; Nghiem, P.; Noels, A.; Oehlinger, J.; Poretti, E.; Provost, J.;
Renan de Medeiros, J.; De Ridder, J.; Rieutord, M.; Roca-Cortes, T.;
Roxburgh, I.; Samadi, R.; Scuflaire, R.; Suarez, J. C.; Theado, S.;
Thoul, A.; Toutain, T.; Turck-Chieze, S.; Uytterhoeven, K.; Vauclair,
G.; Vauclair, S.; Weiss, W. W.; Zwintz, K.
2006ESASP1306...39M Altcode: 2008arXiv0811.1080M
We introduce the main lines and specificities of the CoRoT Seismology
Core Programme. The development and consolidation of this programme has
been made in the framework of the CoRoT Seismology Working Group. With a
few illustrative examples, we show how CoRoT data will help to address
various problems associated with present open questions of stellar
structure and evolution.
---------------------------------------------------------
Title: SIMU-LC: A Light-Curve Simulator for CoRoT
Authors: Baudin, F.; Samadi, R.; Appourchaux, T.; Michel, E.
2006ESASP1306..403B Altcode:
In order to prepare the analysis of COROT data, it has been decided
to build a simple tool to simulate the expected light curves. This
simulation tools takes into account both instrumental constraints and
astrophysical inputs for the COROT targets. For example, granulation and
magnetic activity signatures are simulated, as well as p modes, with
the expected photon noise. However, the simulations rely sometimes on
simple approach of these phenomenons, as the main goal of this tool is
to prepare the analysis in the case of COROT data and not to perform
the most realistic simulations of the different phenomenons.
---------------------------------------------------------
Title: The internal structure of the Sun inferred from g modes and
low-frequency p modes
Authors: Elsworth, Y. P.; Baudin, F.; Chaplin, W; Andersen, B;
Appourchaux, T.; Boumier, P.; Broomhall, A. -M.; Corbard, T.;
Finsterle, W.; Fröhlich, C.; Gabriel, A.; García, R. A.; Gough,
D. O.; Grec, G.; Jiménez, A.; Kosovichev, A.; Provost, J.; Sekii,
T.; Toutain, T.; Turck-Chièze, S.
2006ESASP.624E..22E Altcode: 2006soho...18E..22E
The Phoebus group is an international collaboration of
helioseismologists, its aim being to detect low-frequency solar g
modes. Here, we report on recent work, including the development and
application of new techniques based on the detection of coincidences
in contemporaneous datasets and the asymptotic properties of the g-mode
frequencies. The length of the time series available to the community is
now more than ten years, and this has reduced significantly the upper
detection limits on the g-mode amplitudes. Furthermore, low-degree p
modes can now be detected clearly at frequencies below 1000 μHz.
---------------------------------------------------------
Title: Rotation inversions of artificial solarFLAG Sun-as-a-star data
Authors: Chaplin, W. J.; Sekii, T.; Appourchaux, T.; Baudin, F.;
Boumier, P.; Corbard, T.; Elsworth, Y.; Fletcher, S. T.; Garcia,
R. A.; Jiménez-Reyes, S. J.; Lazrek, M.; New, R.; Salabert, D.;
Toutain, T.; Wachter, R.
2006ESASP.624E..82C Altcode: 2006soho...18E..82C
No abstract at ADS
---------------------------------------------------------
Title: Recent Progresses on g-Mode Search
Authors: Appourchaux, T.; Andersen, B.; Baudin, F.; Boumier, P.;
Broomhall, A. -M.; Chaplin, W.; Corbard, T.; Elsworth, Y.; Finsterle,
W.; Fröhlich, C.; Gabriel, A.; Garcia, R.; Gough, D. O.; Grec, G.;
Jiménez, A.; Kosovichev, A.; Provost, J.; Sekii, T.; Toutain, T.;
Turck-Chièze, S.
2006ESASP.617E...2A Altcode: 2006soho...17E...2A
No abstract at ADS
---------------------------------------------------------
Title: Solar FLAG hare and hounds: on the extraction of rotational
p-mode splittings from seismic, Sun-as-a-star data
Authors: Chaplin, W. J.; Appourchaux, T.; Baudin, F.; Boumier, P.;
Elsworth, Y.; Fletcher, S. T.; Fossat, E.; García, R. A.; Isaak,
G. R.; Jiménez, A.; Jiménez-Reyes, S. J.; Lazrek, M.; Leibacher,
J. W.; Lochard, J.; New, R.; Pallé, P.; Régulo, C.; Salabert, D.;
Seghouani, N.; Toutain, T.; Wachter, R.
2006MNRAS.369..985C Altcode: 2006MNRAS.tmp..515C; 2006astro.ph..6748C
We report on results from the first solar Fitting at Low-Angular
degree Group (solar FLAG) hare-and-hounds exercise. The group
is concerned with the development of methods for extracting the
parameters of low-l solar p-mode data (`peak bagging'), collected by
Sun-as-a-star observations. Accurate and precise estimation of the
fundamental parameters of the p modes is a vital pre-requisite of all
subsequent studies. Nine members of the FLAG (the `hounds') fitted
an artificial 3456-d data set. The data set was made by the `hare'
(WJC) to simulate full-disc Doppler velocity observations of the
Sun. The rotational frequency splittings of the l = 1, 2 and 3 modes
were the first parameter estimates chosen for scrutiny. Significant
differences were uncovered at l = 2 and 3 between the fitted splittings
of the hounds. Evidence is presented that suggests this unwanted bias
had its origins in several effects. The most important came from the
different way in which the hounds modelled the visibility ratio of
the different rotationally split components. Our results suggest that
accurate modelling of the ratios is vital to avoid the introduction of
significant bias in the estimated splittings. This is of importance
not only for studies of the Sun, but also of the solar analogues
that will be targets for asteroseismic campaigns. <P />Solar FLAG
URL: http://bison.ph.bham.ac.uk/~wjc/Research/FLAG.html <P />E-mail:
wjc@bison.ph.bham.ac.uk ‡ <P />George Isaak passed away in 2005 June
5, prior to the completion of this work. He is greatly missed by us all.
---------------------------------------------------------
Title: Can we finally solve the problems of "Coronal Heating " and
"Solar Wind Acceleration" in the Cosmic Vision era ?
Authors: Maksimovic, M.; Appourchaux, T.; Aulanier, G.; Chust, T.;
Dudok de Wit, T.; Klein, K. L.; Krasnoselskikh, V.; Louarn, P.; Roux,
A.; Vial, J. C.
2006cosp...36.2999M Altcode: 2006cosp.meet.2999M
Since the discovery of the corona s million-degree temperature in the
1940s and the supersonic solar wind in the early 1960s major efforts
have been made to discover the physical mechanisms that could explain
these two observations These efforts have led to a tremendous increase
in our knowledge of our neighbour star the inner heliosphere and the
Sun-Earth connections Unfortunately these efforts haven t allowed to
provide a definitive answer to these questions Why such a situation On
one hand the remote-sensing strategy has tried to probe the coronal
properties by basically analysing the photons emitted or absorbed
by the Sun s atmosphere With this regards limitations occur on both
theoretical ground physics of the coupling between photons and plasma
and experimental ground limited number of observables such as spectral
lines or the hardly solvable problem of the line of sight integration
On the other hand solar wind in-situ measurements have had access to
the very detailed state of the local plasma properties full particles
velocity distribution functions observations of the electromagnetic
plasma fluctuations over a huge frequency range but at locations
far from the corona and the solar wind acceleration regions Moreover
it has been realized more recently that the magnetic field plays a
fundamental role in shaping the low corona and channelling the energy
inputs Unfortunately the measurement of the full magnetic vector in
the corona is a very difficult enterprise and this lack of information
hampers all on-going modelling efforts Given
---------------------------------------------------------
Title: The Beleinos cornerstone: the Sun, the star close to Earth
Authors: Appourchaux, T.; Auchère, F.; Bocchialini, K.; Bonnet,
R. M.; Gabriel, A.; Vial, J. -C.
2005ESASP.588..389A Altcode: 2005tssc.conf..389A
No abstract at ADS
---------------------------------------------------------
Title: The magnetism of the solar interior for a complete MHD
solar vision
Authors: Turck-Chièze, S.; Appourchaux, T.; Ballot, J.; et al.
2005ESASP.588..193T Altcode: 2005astro.ph.10854T; 2005tssc.conf..193T
The solar magnetism is no more considered as a purely superficial
phenomenon. The SoHO community has shown that the length of the
solar cycle depends on the transition region between radiation and
convection. Nevertheless, the internal solar (stellar) magnetism
stays poorly known. Starting in 2008, the American instrument HMI/SDO
and the European microsatellite PICARD will enrich our view of the
Sun-Earth relationship. Thus obtaining a complete MHD solar picture is
a clear objective for the next decades and it requires complementary
observations of the dynamics of the radiative zone. For that ambitious
goal, space prototypes are being developed to improve gravity mode
detection. The Sun is unique to progress on the topology of deep
internal magnetic fields and to understand the complex mechanisms which
provoke photospheric and coronal magnetic changes and possible longer
cycles important for human life. We propose the following roadmap in
Europe to contribute to this "impressive" revolution in Astronomy and
in our Sun-Earth relationship: SoHO (1995-2007), PICARD (2008-2010),
DynaMICS (2009-2017) in parallel to SDO (2008-2017) then a world-class
mission located at the L1 orbit or above the solar poles.
---------------------------------------------------------
Title: Working group report on Asteroseismology and stellar activity
from Dome C
Authors: Bouchy, F.; Mosser, B.; Catala, C.; Appourchaux, T.; Bouvier,
J.; Chadid, M.; Donati, J. F.; Fossat, E.; Schmider, F. X.; Thevenin,
F.; Vauclair, G.
2005sf2a.conf..329B Altcode:
This paper presents the conclusions of the working group for stellar
physics observations at the Dome-C station in Antarctica. It summarizes
the advantages of Dome-C for asteroseismology and stellar activity,
identifies strategies and possible instrumental projects to be conducted
there, and concludes with recommendations for the development of stellar
observations. The conclusions are based on the fact that continuous
observations over several weeks or months without breaks due to the
diurnal cycle are fundamental for programs of stellar physics and
especially for asteroseismology and stellar activity. Therefore, Dome-C
appears to be a unique ground-based site offering ideal conditions
for continuous observations.
---------------------------------------------------------
Title: The life of stars and their planets
Authors: Catala, C.; Aerts, C.; Aigrain, S.; Antonello, E.;
Appourchaux, T.; Auvergne, M.; Baglin, A.; Barge, P.; Barstow, M. A.;
Baudin, F.; Boumier, P.; Collier Cameron, A.; Christensen-Dalsgaard,
J.; Cutispoto, G.; Deeg, H.; Deleuil, M.; Desidera, S.; Donati, J. -F.;
Favata, F.; Foing, B. H.; Gameiro, J. F.; Garcia, R.; Garrido, F.;
Horne, K.; Lanza, A. F.; Lanzafame, A. C.; Lecavelier Des Etangs,
A.; Léger, A.; Mas-Hesse, M.; Messina, S.; Micela, G.; Michel, E.;
Monteiro, M. J. P. F. G.; Mosser, B.; Noels, A.; Pagano, I.; Piotto,
G.; Poretti, E.; Rauer, H.; Roca-Cortes, T.; Rodono, M.; Rouan, D.;
Roxburgh, I.; Schneider, J.; Strassmeier, K.; Turck-Chièze, S.;
Vauclair, S.; Vidal-Madjar, A.; Weiss, W. W.; Wheatley, P.
2005ESASP.588...99C Altcode: 2005tssc.conf...99C
We lack a reliable scenario for the formation and evolution of stars
and their planetary systems, involving key factors such as magnetic
fields and turbulence. We present the case for a mission concept that
will clarify these problems and give us a global view of the evolution
of combined star and planetary systems. This will be achieved by
simultaneously addressing the search for planetary transits in front
of a large number of stars, including many nearby stars, the study of
their internal structure and evolution via asteroseismology, and that
of their magnetic activity, via UV monitoring.
---------------------------------------------------------
Title: The luminosity oscillations imager, a space instrument:
from design to science
Authors: Appourchaux, Thierry
2005pmds.book..185A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Innovative designs for the imaging suite on Solar Orbiter
Authors: Auchere, Frederic; Song, Xueyen; Rouesnel, Frederic;
Appourchaux, Thierry; Fourmon, Jean-Jacques; Le Clec'h,
Jean-Christophe; Berthe, Michel; Defise, Jean-Marc; Mazy, Emmanuel;
Rochus, Pierre L.; Mercier, Raymond; Ravet, Marie-Francoise
2005SPIE.5901..298A Altcode:
Orbiting around the Sun on an inclined orbit with a 0.2 UA perihelion,
the Solar Orbiter probe will provide high resolution views of the Sun
from various angles unattainable from Earth. Together with a set of high
resolution imagers, the Full Sun Imager is part of the EUV Imaging suite
of the Solar Orbiter mission. The mission's ambitious characteristics
draw severe constraints on the design of these instruments. We present
a photometrically efficient, compact, and lightweight design for the
Full Sun Imager. With a 5 degrees field of view, this telescope will
be able to see the global solar coronal structure from high viewing
angles. Thermal solutions reducing the maximum power trapped in the
High Resolution Imagers are also proposed.
---------------------------------------------------------
Title: Inferred acoustic rates of solar p modes from several
helioseismic instruments
Authors: Baudin, F.; Samadi, R.; Goupil, M. -J.; Appourchaux, T.;
Barban, C.; Boumier, P.; Chaplin, W. J.; Gouttebroze, P.
2005A&A...433..349B Altcode:
Acoustic rates of excitation of solar p modes can be estimated from
observations in order to place constraints on the modelling of the
excitation process and the layers where it occurs in the star. For
several reasons (including a poor signal to noise ratio and mode
overlap), this estimation is difficult. In this work, we use three
completely independent datasets to obtain robust estimates in the
solar case for ℓ=1 modes. We also show that the height in the solar
atmosphere where the modes are observed must be taken into account. Our
three sets of results are shown to be consistent, particularly in
the lower part of the p-mode spectrum (from 1.8 mHz to 2.8 mHz). At
higher frequencies, the agreement is not as good, because of a larger
dispersion of the measurements and also because of some systematic
differences which might be due to observation height estimation or to
a systematic influence of the noise.
---------------------------------------------------------
Title: On measuring planetary winds using high-resolution spectroscopy
in visible wavelengths
Authors: Civeit, T.; Appourchaux, T.; Lebreton, J. -P.; Luz, D.;
Courtin, R.; Neiner, C.; Witasse, O.; Gautier, D.
2005A&A...431.1157C Altcode:
We present a new method that uses high-resolution spectroscopy in
the visible wavelength domain to measure planetary winds. A rotating
atmosphere illuminated by the Sun induces a Doppler shift in the
back-scattered solar light. Its analysis with a cross-dispersed echelle
spectrometer allows the direct determination of both the wind speed
and direction. We describe in this paper the image and data processing
algorithms used in the method and implemented in a data reduction
and analysis package. Since the velocity of planetary winds leads to
Doppler shifts smaller than the width of the solar lines, accurate
Doppler measurements are performed by running the algorithm proposed
by [CITE], which is an optimum technique using the full available
spectral information. We apply the method to Io as a test case, a
small slowly-rotating body with no atmosphere, to measure its solid
rotation. The observations span wavelengths from 414 to 621 nm and were
carried out with the Ultraviolet and Visual Echelle Spectrograph (UVES)
on the 8.2 m Kueyen unit at the Very Large Telescope (VLT ESO). The
results we obtain for Io validate the principle of the method by
optimally measuring the well-known surface rotational velocity of this
moon, with an uncertainty smaller than 2 m s<SUP>-1</SUP>. However,
the analysis of the set of observations shows that systematic errors are
large and one needs to consider the retrieved velocity as a lower limit.
---------------------------------------------------------
Title: On the detection of pure sine waves embedded in a spectrum
of stochastically excited p modes
Authors: Moreira, O.; Appourchaux, T.; Berthomieu, G.; Toutain, T.
2005MNRAS.357..191M Altcode: 2005MNRAS.tmp...16M
The mode identification and fitting of solar oscillations provide
an observational tool to derive the physical properties of the Sun's
interior. What has been devised for helioseismology can now be used for
future asteroseismology ground-based instruments and space missions,
such as the High-Accuracy Radial Velocity Planetary Searcher (HARPS)
and Convection, Rotation and Planetary Transits (COROT). In the coming
decade, numerous stars will be observed for which new tools will be
needed. For instance, it is very likely that g and p modes will be
detected, rendering the identification difficult. In addition, modes
having both characteristics, known as mixed modes, are also likely to
be detected in evolved stars; these latter modes are crucial for the
understanding of the internal structure of the stars as they propagate
deeply inside the stars, unlike the p modes. Unfortunately, the mixing
will not only occur physically but also in the frequency domain: mixed
modes will appear very close to stochastically excited p modes. In this
paper, we have devised a new technique for detecting long-lived modes
(mixed or g modes) embedded in a common p-mode spectrum. The technique
has been validated using Monte Carlo simulations. In the framework of
the hare-and-hound exercise of COROT, this technique has been applied
to synthetic time series of the evolved solar-like star HD 57006. The
results show that we can detect most of the mixed modes embedded by
the hare. We also discuss the impact of how the long-lived modes are
excited on the detection level. The technique described here can be
applied to stars with a mass greater than 1.2 M<SUB>solar</SUB>, having
evolved possibly beyond the terminal-age main sequence, such as Procyon.
---------------------------------------------------------
Title: Characterization of the Zonal Wind Flow in the Upper Atmosphere
of Titan with the VLT
Authors: Courtin, Régis; Luz, David; Gautier, Daniel; Appourchaux,
Thierry; Lebreton, Jean-Pierre; Ferri, Francesca; Lara, Luisa; Hourdin,
Frédéric; Kaufer, Andreas
2005HiA....13..897C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On detecting short-lived p modes in a stellar oscillation
spectrum
Authors: Appourchaux, T.
2004A&A...428.1039A Altcode:
The false alarm probability for detecting peaks embedded in a power
spectrum of noise was given by \cite{Scargle82}. This test has been
used in helioseismology to detect long-lived modes such as g modes
\citep{TA2000}. With the development of asteroseismology, there is
now a need to define a similar test but for short-lived p modes. In
this article, I define a false alarm test for detecting short-lived p
modes, and I give the probability of detecting such modes given their
signal-to-noise ratio, their linewidths and the duration of observation.
---------------------------------------------------------
Title: Flag Hare-And Exercise: on the Extraction of Sectoral Mode
Splittings from Full-Disc Sun-As Data
Authors: Chaplin, W. J.; Appourchaux, T.; Baudin, F.; Boumier, P.;
Elsworth, Y.; Fletcher, S. T.; Fossat, E.; García, R. A.; Isaak,
G. R.; Jiménez, A.; Jiménez-Reyes, S. J.; Lazrek, M.; Lochard, J.;
New, R.; Pallé, P.; Régulo, C.; Salabert, D.; Toutain, T.
2004ESASP.559..356C Altcode: 2004soho...14..356C
No abstract at ADS
---------------------------------------------------------
Title: a Radial Velocity Search for P-Modes in VIR
Authors: Martic, M.; Lebrun, J. C.; Appourchaux, T.; Schmitt, J.
2004ESASP.559..563M Altcode: 2004astro.ph..9126M; 2004soho...14..563M
Spectroscopic high-resolution observations were performed with
fiber-fed cross-dispersed echelle spectrographs in order to measure
the fluctuations in radial velocities of a sample of bright stars
that are likely to undergo solar-like oscillations. Here we report
the results for beta Vir (HR4540) from two observing runs carried out
in February 2002 with FEROS at the ESO 1.52 m telescope in La Silla
(Chile) and ELODIE spectrograph at 1.93 OHP telescope (Observatoire de
Haute Provence, France). The analysis of the time series of Doppler
shifts from both sites has revealed the presence of an excess power
around 1.7 mHz. We discuss the interpretation of this data set in
terms of possible p-mode oscillations.
---------------------------------------------------------
Title: On comparing estimates of low-l solar p-mode frequencies from
Sun-as-a-star and resolved observations
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Isaak, G. R.;
Miller, B. A.; New, R.
2004A&A...424..713C Altcode:
Low-angular-degree (low-l) solar p modes provide a sensitive probe
of the radiative interior and core of the Sun. Estimates of their
centroid frequencies can be used to constrain the spherically symmetric
structure of these deep-lying layers. The required data can be extracted
from two types of observation: one where the modes are detected in
integrated sunlight, i.e., a Sun-as-a-star view; and a second where
the visible disc is imaged onto many pixels, and the collected images
then decomposed into their constituent spherical harmonics. While the
imaging strategy provides access to all of the individual components
of a multiplet, the Sun-as-a-star technique is sensitive to only
about two thirds of these (average over l=0 to 3) with those modes
that are detected having different levels of visibility. Because
the various components can have contrasting spatial structure over
the solar surface, they can respond very differently to changes in
activity along the solar cycle. Since the Sun-as-a-star and resolved
analyses take as input a different “subset” of modes, the extracted
frequency estimates are expected to differ depending upon the phase
of the cycle. Differences also arise from the types of models used to
fit the modes. Here, we present expressions that allow the sizes of
these differences to be predicted.
---------------------------------------------------------
Title: p-mode frequencies in solar-like stars. I. Procyon A
Authors: Martić, M.; Lebrun, J. -C.; Appourchaux, T.; Korzennik, S. G.
2004A&A...418..295M Altcode: 2004astro.ph..3035M
As a part of an on-going program to explore the signature of p-modes
in solar-like stars by means of high-resolution absorption line
spectroscopy, we have studied four stars (α CMi, η Cas A, ζ Her A
and β Vir). We present here new results from two-site observations of
Procyon A acquired over twelve nights in 1999. Oscillation frequencies
for l=1 and 0 (or 2) p-modes are detected in the power spectra of
these Doppler shift measurements. A frequency analysis points out the
difficulties of the classical asymptotic theory in representing the
p-mode spectrum of Procyon A. <P />Based on observations obtained at
the Observatoire de Haute-Provence (CNRS, France) and at the Whipple
Observatory (Arizona, USA).
---------------------------------------------------------
Title: Solar p-mode frequencies at ℓ=2: What do analyses of
unresolved observations actually measure?
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Isaak, G. R.;
Miller, B. A.; New, R.; Toutain, T.
2004A&A...416..341C Altcode:
We have studied in detail the extraction of estimates of ℓ=2 p-mode
frequencies from unresolved observations of the visible disc of the
Sun. Examples of data of this type include ground-based observations
made by the Birmingham Solar-Oscillations Network (BiSON), and
space-borne observations made by the GOLF and VIRGO/SPM instruments
on board the ESA/NASA SOHO satellite. The fitting of the modes is
complicated in practice by the asymmetric arrangement in frequency
of the three components (m=-2, 0 and 2) that are prominent in such
data. In order to investigate the effect of this we used a series of
10-yr artificial datasets into which varying degrees of asymmetry were
introduced. The sets were designed to mimic the characteristics of the
BiSON and GOLF data, and were analyzed both with and without the BiSON
window function from the period 1992 through 2001. Since reliable
estimates of the asymmetry have only recently been extracted from
unresolved observations (Chaplin et al. \cite{Chaplin03}a) it has for a
long time been standard practice to fit the ℓ=2 modes to a model that
assumes a symmetrically arranged multiplet. We have tested the impact
of this on the accuracy of the extracted frequencies. Furthermore,
we demonstrate that asymmetric models can be successfully applied,
provided the data are of sufficient length and quality. We also discuss
the implications of our simulations for analyses of real solar data.
---------------------------------------------------------
Title: Development of imaging arrays for solar UV observations based
on wide band gap materials
Authors: Schuehle, Udo H.; Hochedez, Jean-Francois E.; Pau, Jose Luis;
Rivera, Carlos; Munoz, Elias; Alvarez, Jose; Kleider, Jean-Paul;
Lemaire, Philippe; Appourchaux, Thierry; Fleck, Bernhard; Peacock,
Anthony; Richter, Mathias; Kroth, Udo; Gottwald, Alexander; Castex,
Marie-Claude; Deneuville, Alain; Muret, Pierre; Nesladek, Milos;
Omnes, Franck; John, Joachim; Van Hoof, Chris
2004SPIE.5171..231S Altcode:
Solar ultraviolet imaging instruments in space pose most demanding
requirements on their detectors in terms of dynamic range, low noise,
high speed, and high resolution. Yet UV detectors used on missions
presently in space have major drawbacks limiting their performance
and stability. In view of future solar space missions we have started
the development of new imaging array devices based on wide band gap
materials (WBGM), for which the expected benefits of the new sensors -
primarily visible blindness and radiation hardness - will be highly
valuable. Within this initiative, called "Blind to Optical Light
Detectors (BOLD)", we have investigated devices made of AlGa-nitrides
and diamond. We present results of the responsivity measurements
extending from the visible down to extreme UV wavelengths. We discuss
the possible benefits of these new devices and point out ways to build
new imaging arrays for future space missions.
---------------------------------------------------------
Title: Global fitting of power spectra of solar-like stars
Authors: Neiner, C.; Appourchaux, T.
2004ESASP.538..373N Altcode: 2004sshp.conf..373N
Helioseismology has been able to provide the internal structure of
the Sun and its dynamics. These inferences have been made possible
by inverting the frequencies and rotational splitting of the p-mode
oscillations. Thanks to asteroseismology, similar results can now
be obtained for stars other than the Sun. For this purpose, we are
developing a numerical code for global fitting of power spectra. The
code is currently developed and tested on full-disk integrated solar
data obtained with the SOHO/LOI instrument. It will then be applied to
synthetic data from the hare-and-hound exercises of COROT. The final
goal is to apply the technique to data of solar-like stars obtained
with the COROT and Eddington satellites to infer the internal structure
and dynamics of those stars.
---------------------------------------------------------
Title: Mode extraction from time series: from the challenges of
COROT to those of Eddington
Authors: Appourchaux, T.; Moreira, O.; Berthomieu, G.; Toutain, T.
2004ESASP.538..109A Altcode: 2004sshp.conf..109A
With more than 30 years of experience in extraction of eigenmodes from
power spectra of solar signals, we are now almost ready to apply this
knowledge onto the forecoming missions: COROT and Eddington. However the
fitting task differs by 3 orders of magnitude; COROT will be able to get
time series of stellar light for some 30 stars, while Eddington will
be able to gather such data for about 50000 stars. While for COROT,
our current tools can be applied by hand, the case of Eddington is
significantly more complex. We are looking forward having automatic
fitting procedures that will allow to recover mode parameters for about
90% of the solar-like stars. Unfortunately, about 10% of these stars
will require some more delicate attention that will cost time to take
care of. We will use the example of the infamous HD 57006, known to
be quite evolved with a difficult eigenmode spectrum, to explain how
a star can evolve from an easy-to-fit target (90% of the solar-like
stars) to a difficult-to-fit (10% of the remaining stars). In the
latter case, new techniques for detecting narrow peaks (g-mode like)
out of broad peaks (p-mode like) has been devised in the context of
the hare-and-hound exercise of COROT. This and other techniques will be
used to implement the automatic fitting procedure for the remaining 10%
of Eddington solar-like stars.
---------------------------------------------------------
Title: On Maximum Likelihood Estimation of averaged power spectra
Authors: Appourchaux, T.
2003A&A...412..903A Altcode:
It is custom in helioseismology to assume that the power spectra of
time series of solar radial velocity or of solar intensity have a
χ<SUP>2</SUP> with 2 degrees of freedom statistics. This assumption
is regularly used in helioseismology for using Maximum Likelihood
Estimators for single power spectra with that assumed statistics. When
independent power spectra are added, it is also custom to assume
that the resulting power spectra can be approximated by a Gaussian
distribution. Here we show that this approximation is irrelevant,
and that the software code developed for fitting single power spectra
can be used without any approximation after proper normalization of
the added power spectra.
---------------------------------------------------------
Title: Characterization of the zonal wind in Titan's stratosphere
with UVES
Authors: Luz, D.; Courtin, R.; Gautier, D.; Appourchaux, T.; Ferri,
F.; Lebreton, J. -P.; Lara, L.; Hourdin, F.; Kaufer, A.
2003EAEJA.....2941L Altcode:
We will report on recent efforts to characterize the zonal wind flow
in Titan's stratosphere. We have used the UVES echelle spectrometer
mounted at VLT-UT2 to obtain high-resolution solar spectra reflected
off Titan. The purpose of the observations, which were done in February
2002, has been to detect the differential Doppler shift induced by the
zonal wind flow in the back-scattered solar radiation from the East and
West limbs of Titan. Since the wind speed should not exceed 200 m/s,
an absolute detection of the shift on single solar lines is not feasible
due to the limited spectral resolution of UVES. This is why we apply a
retrieval scheme developed for stellar accelerometry (Connes P. 1985,
ApSS 110, 211; Martyc M. et al. 1999, A&A 351, 993) which makes
use of the full spectral range (∼ 4200 to 6200 Angstroms for the red
arm of the instrument) and takes into account all the lines present
in the spectrum. Preliminary results indicate that the wind is prograde.
---------------------------------------------------------
Title: The search for g modes
Authors: Appourchaux, T.
2003ESASP.517..131A Altcode: 2003soho...12..131A
The Phoebus group was set up about 5 years ago with the expressed
purpose to detect the g modes predicted by helioseismology to occur in
the sun. The current status will be reviewed including new approaches
proposed by other groups in the field. Over the years, the upper limit
to g-mode amplitude set by Appourchaux et al. (2000) (10 mm/s at 10 σ)
has been lowered due to a longer time series as well as new detection
techniques. Not withstanding these efforts the chance of a positive
detection still appears remote with the current upper limit still way
above that predicted by helioseismology. New techniques in particular
observations involving limb intensity and/or velocity cross-correlations
against various observables, or even the detection of gravitational
waves may offer the best hope for a future positive detection.
---------------------------------------------------------
Title: New UV detectors for solar observations
Authors: Hochedez, Jean-Francois E.; Schuehle, Udo H.; Pau, Jose L.;
Alvarez, Jose; Hainaut, Olivier; Appourchaux, Thierry P.; Auret, F. D.;
Belsky, Andrei; Bergonzo, Philippe; Castex, M. C.; Deneuville, A.;
Dhez, Pierre; Fleck, Bernhard; Haenen, Ken; Idir, Mourad; Kleider,
Jean Paul; Lefeuvre, Elie; Lemaire, Philippe; Monroy, E.; Muret, P.;
Munoz, Elias; Nesladek, Milos; Omnes, Franck; Pace, Emanuele; Peacock,
Anthony J.; Van Hoof, Chris A.
2003SPIE.4853..419H Altcode:
BOLD (Blind to the Optical Light Detectors) is an international
initiative dedicated to the development of novel imaging detectors
for UV solar observations. It relies on the properties of wide bandgap
materials (in particular diamond and Al-Ga-nitrides). The investigation
is proposed in view of the Solar Orbiter (S.O.) UV instruments, for
which the expected benefits of the new sensors -primarily visible
blindness and radiation hardness- will be highly valuable. Despite
various advances in the technology of imaging detectors over the last
decades, the present UV imagers based on silicon CCDs or microchannel
plates exhibit limitations inherent to their actual material
and technology. Yet, the utmost spatial resolution, fast temporal
cadence, sensitivity, and photometric accuracy will be decisive for
the forthcoming solar space missions. The advent of imagers based on
wide-bandgap materials will permit new observations and, by simplifying
their design, cheaper instruments. As for the Solar Orbiter, the
aspiration for wide-bandgap material (WBGM) based UV detectors is still
more sensible because the spacecraft will approach the Sun where the
heat and the radiation fluxes are high. We describe the motivations,
and present the program to achieve revolutionary flight cameras within
the Solar Orbiter schedule as well as relevant UV measurements.
---------------------------------------------------------
Title: Characterization of Titan's Zonal Wind Flow with the VLT
Authors: Courtin, Regis; Luz, D.; Gautier, D.; Appourchaux, T.; Ferri,
F.; Lebreton, J. -P.; Lara, L.; Hourdin, F.; Kaufer, A.
2003IAUSS...1E..33C Altcode:
We will report on recent efforts to characteize the zonal wind flow in
Titan's upper atmosphere. We used the UVES echelle spectrometer at the
focus of the VLT-UT2 to obtain high-resolution Titan raeflection spectra
in the visible from 420 to 630 nm. The purpose of the observations
which were carried out in February 2002 was to detect the differential
Doppler shift induced by the zonal wind flowin the back-scattered solar
radiation from the Eastern and Western limbs of Titan. The measured
spectra were analyzed withthe help of a velocity retrieval scheme
developed for stellar accelerometry taking into account all of the
solar lines present in the observed spectral range (Connes 1985 ApSS
110 211; Martyc et al. 1999 AA 351 993). Preliminary results indicate
that the wind is prograde and that the wind speed is consistent with
model predictions.
---------------------------------------------------------
Title: Observations of the Sun's magnetic field during the recent
solar maximum
Authors: Sanderson, T. R.; Appourchaux, T.; Hoeksema, J. T.; Harvey,
K. L.
2003JGRA..108.1035S Altcode:
We present new observations and analyses of the Sun's magnetic field and
coronal holes. Using magnetic field observations from the Wilcox Solar
Observatory, we present a simple means whereby the tilt angle of the
current sheet can be calculated. We use a data set covering the last 26
years, which shows for the first time how the dipole component rotated
once during a full 22-year solar cycle. We show how this influenced
the current sheet. At solar minimum, the Sun's coronal magnetic field
was essentially dipolar and aligned parallel to the spin axis. As a
result, the heliospheric current sheet was flat and had very little
warp. Around solar maximum, the dipole was perpendicular to the spin
axis, and the ratio of quadrupole to dipole strength was high for much
of the time. This meant that the current sheet was tilted and highly
warped, and reached up to high latitudes. Surprisingly, there were
also times close to solar maximum when the quadrupole/dipole ratio
was low, and the current sheet was relatively flat, but still highly
inclined. We apply for the first time to solar magnetic data a method,
which quantitatively analyses the quadrupole component of the magnetic
field. From the terms of the expansion of the observed photospheric
magnetic field, we compute the position of the poles of the magnetic
field. We combine for the first time over an extended period of time
magnetic field data from the Wilcox Solar Observatory with coronal
hole positions taken from the National Solar Observatory/Kitt Peak. We
find that the position of the coronal holes followed the motion of the
poles of the magnetic field as the poles moved over the surface of the
Sun and that the polar coronal holes broke up into groups of smaller
like-polarity holes as the poles approached the midlatitude regions
and the quadrupole became more important. We discuss the implications
for energetic particle observations at Ulysses.
---------------------------------------------------------
Title: Peak Bagging for Solar-like Stars
Authors: Appourchaux, Thierry
2003Ap&SS.284..109A Altcode:
The identification of the low-degree p modes in other stars is the
challenge of future asteroseismology space missions such as COROT,
MONS, MOST or Eddington. The identification is based on a priori
knowledge of the characteristics of the modes. We shall review the most
common assumptions needed for the identification such as basic stellar
structure, visibilities, rotational splittings or linewidths. We shall
describe a few tools needed for facilitating the identification. As
soon as modes are properly identified, the peakbagging of the mode
characteristics can be done using Maximum Likelihood Estimation. We
give examples of the whole process using solar data and hare-and-hound
exercises performed in the frame work of the COROT project.
---------------------------------------------------------
Title: Hare &Hound Exercise with Simulated COROT Data
Authors: Berthomieu, G.; Appourchaux, T.; COROT Seismology Working
Group
2003aahd.conf..465B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Peak finding at low signal-to-noise ratio: low-ℓ solar
acoustic eigenmodes at n≤9 from the analysis of BiSON data
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; Marchenkov,
K. I.; Miller, B. A.; New, R.; Pinter, B.; Appourchaux, T.
2002MNRAS.336..979C Altcode:
We make use of 9 yr of full-disc helioseismic data - as collected by
the ground-based Birmingham Solar-Oscillations Network (BiSON) - to
search for low-frequency, low-angular-degree (low-l) acoustic modes. A
range of tests are applied to the power spectrum of the observations
that search for prominent mode-like structure: strong spikes, structure
spanning several bins signifying the presence of width (from damping),
and the occurrence of prominent multiplet structure at l>= 1 arising
principally from the solar rotation and made from several spikes
separated suitably in frequency. For each test we present analytical
expressions that allow the probability that the uncovered structure is
part of the broad-band noise background to be assessed. These make use
of the cumulative binomial (Bernoulli) distribution and serve to provide
an objective measure of the significance of the detections. This work
has to date uncovered nine significant detections of non-broad-band
origin that we have identified as low-l modes with radial overtone
numbers n<= 9.
---------------------------------------------------------
Title: Characterization of the Zonal Wind Flow in the Stratosphere
of Titan with UVES
Authors: Luz, D.; Courtin, R.; Gautier, D.; Ferri, F.; Appourchaux,
T.; Lebreton, J. -P.; Cabane, M.; Rannou, P.; Hourdin, F.; Lara, L.;
Kaufer, A.
2002DPS....34.3405L Altcode: 2002BAAS...34..901L
We will report on recent efforts to characterize the zonal wind
flow in Titan's stratosphere. We used the UVES echelle spectrometer
at the focus of the UT2 of the Very Large Telescope at Paranal,
Chile, to measure the reflection spectrum of Titan between 4200
and 6200 angstrom with a resolution of 80,000. The purpose of these
observations, which were carried out in February 2002, is to detect
the differential Doppler shift induced by the zonal wind flow between
the East and West limbs of Titan. However, because the wind speed is
not expected to exceed 200 m/s, an absolute detection of the Doppler
shift on isolated solar lines is not feasible, even at the spectral
resolution of UVES. Therefore, we have made use of a retrieval scheme
developed for absolute stellar accelerometry (Connes 1985, ApSS 110,
211; Martic et al. 1999, A&A 351, 993) to extract the velocity
signal by simultaneously taking into account all the lines present
in the spectrum. We will describe the method and discuss preliminary
results. Research supported by the "Programme National de Planetologie"
of the Institut National des Sciences de l'Univers (France). D. Luz
acknowledges financial support by the Portuguese Foundation for Science
and Technology, ref.SFRH-BPD-3630-2000.
---------------------------------------------------------
Title: A search for solar g modes in the GOLF data
Authors: Gabriel, A. H.; Baudin, F.; Boumier, P.; García, R. A.;
Turck-Chièze, S.; Appourchaux, T.; Bertello, L.; Berthomieu, G.;
Charra, J.; Gough, D. O.; Pallé, P. L.; Provost, J.; Renaud, C.;
Robillot, J. -M.; Roca Cortés, T.; Thiery, S.; Ulrich, R. K.
2002A&A...390.1119G Altcode:
With over 5 years of GOLF data having some 90% continuity, a new
attempt has been made to search for possible solar g modes. Statistical
methods are used, based on the minimum of assumptions regarding the
solar physics; namely that mode line-widths are small compared with
the inverse of the observing time, and that modes are sought in the
frequency interval 150 to 400 mu Hz. A number of simulations are carried
out in order to understand the expected behaviour of a system consisting
principally of a solar noise continuum overlaid with some weak sharp
resonances. The method adopted is based on the FFT analysis of a time
series with zero-padding by a factor of 5. One prominent resonance at
284.666 mu Hz coincides with a previous tentative assignment as one
member of an n=1, l=1, p-mode multiplet. Components of two multiplets,
previously tentatively identified as possible g-mode candidates from
the GOLF data in 1998, continue to be found, although their statistical
significance is shown to be insufficient, within the present assumption
regarding the nature of the signal. An upper limit to the amplitude
of any g mode present is calculated using two different statistical
approaches, according to either the assumed absence (H0 hypothesis)
or the assumed presence (H1 hypothesis) of a signal. The former yields
a slightly lower limit of around 6 mm/s.
---------------------------------------------------------
Title: What have we learnt with the Luminosity Oscillations Imager
over the past 6 years?
Authors: Appourchaux, T.; Andersen, B.; Sekii, T.
2002ESASP.508...47A Altcode: 2002soho...11...47A
We summarize what we achieved with 6 years of LOI data. We present
old as well as new results regarding the p-mode parameters dependence
upon solar activity. We have also derived the dependence of the solar
background noise upon solar activity and solar disk position. Inversions
done using LOI frequencies and higher-degree mode frequencies from
GONG confirm previous velocity inversions.
---------------------------------------------------------
Title: Observations of The Sun's Coronal Magnetic Field and Coronal
Holes During The Ulysess Fast Latitude Scan
Authors: Sanderson, T. R.; Appourchaux, T.; Hoeksema, J. T.; Harvey,
K. L.
2002EGSGA..27..595S Altcode:
We have combined magnetic field observations from the Wilcox
Solar Observatory and coronal holes observations from the Kitt Peak
Observatory to investigate how the Sun's magnetic field behaved during
the Ulysses fast latitude scan. <P />Using the dipole and quadrupole
terms in the expansion of the coronal magnetic field, we show that the
dipole rotated once every 22-year solar cycle and that the quadrupole
term reached a maximum at the time of solar maximum. At solar minimum,
the current sheet was flat and had very little warp, but around solar
maximum, during the second Ulysses Southern Polar Pass, the ratio
of quadrupole to dipole strength was high for much of the time. The
current sheet was tilted and highly warped, and reached up to high
latitudes. Surprisingly, there were times when the quadrupole/dipole
ratio was low, and the current sheet was relatively flat, but still
highly inclined. <P />The site of coronal holes follows the motion of
the poles of the magnetic field as the poles move over the surface
of the Sun. The polar coronal hole breaks up into groups of smaller
like-polarity holes as the poles approach the mid-latitude regions.
---------------------------------------------------------
Title: Variation of acoustic mode centroid frequencies over the
solar cycle
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Isaak, G. R.;
New, R.
2002AdSpR..29.1881C Altcode:
Together with a brief historical overview, we use high-quality
helioseismic data collected by three different observational
programmes during the declining phase of activity cycle 22, and a
substantial portion of the rising phase of the current cycle (23),
to study the phenomenological nature of the cycle-induced (centroid)
eigenfrequencies. Our analyses (for 1600 ≤ ν ≤ 4000 μHz) make
use of observations made by the ground-based GONG over the angular
degree range 4 ≤ l ≤ 150; the ground-based BiSON over 0 ≤ l ≤
2; and the VIRGO/LOI instrument on board the ESA/NASA SOHO satellite
over 0 ≤ l ≤ 8. We show that GONG shifts averaged over different
ranges in l, together with the BiSON and LOI data averaged over
their full quoted ranges, all scale at a given frequency with the
normalized mode inertia ratio Q<SUB>nl</SUB> (Christensen-Dalsgaard
& Berthomieu 1991). This is to be expected if the time-dependent
perturbation affecting the modes is confined in the surface layers;
the excellent agreement also reflects favourably on the external
consistency of the different observations. We have also analyzed
the frequency dependence of the shifts by fitting a power-law of the
form δν <SUB>nl</SUB> ∝ (ν <SUB>nl</SUB>/ E<SUB>nl</SUB> to the
data (where the E<SUB>nl</SUB> are the mode inertias, and α is the
power-law index to be extracted). Previous studies have suggested that
a relation with α = 0 provides an adequate description of the shifts
up to ν ≈ 3500 μHz. However, here we show that while nevertheless
describing the shifts well up to ∼ 2500 μHz, the linear scaling
breaks down conspicuously at higher frequencies. Above this threshold,
the shifts follow a power-law dependence with α ∼ 2.
---------------------------------------------------------
Title: Observations of the Sun's Coronal Magnetic Field and Coronal
Holes during the Recent Ulysess Second Polar Pass, and Implications
for Particle Observations
Authors: Sanderson, T. R.; Appourchaux, T.; Hoeksema, J. T.; Harvey,
K. L.
2001AGUFMSH32A0723S Altcode:
We combine magnetic field observations from the Wilcox Solar Observatory
and coronal hole observations from the National Solar Observatory/ Kitt
Peak. At solar minimum, the Sun's coronal magnetic field was dipolar and
aligned along the spin axis. The current sheet was flat and had very
little warp. Around solar maximum, during the second Ulysses southern
polar pass, the ratio of quadrupole to dipole strength was high for
much of the time. This meant that the current sheet was tilted and
highly warped, and reached up to high latitudes. Using the dipole and
quadrupole terms from the expansion of the coronal magnetic field,
we compute the position of the dipole and quadrupole poles. We find
that the location of coronal holes follows the motion of the poles
of the magnetic field as the poles move across the surface of the
Sun. The polar coronal holes break up into groups of smaller holes
all with the same polarity as the poles approach the mid-latitude
regions. Surprisingly, there were also times close to solar maximum
when the quadrupole/dipole ratio was low, and the current sheet was
relatively flat, but still highly inclined. We discuss the implications
for the observations of energetic particles at Ulysses.
---------------------------------------------------------
Title: Changes in convective properties over the solar cycle: effect
on p-mode damping rates
Authors: Houdek, G.; Chaplin, W. J.; Appourchaux, T.;
Christensen-Dalsgaard, J.; Däppen, W.; Elsworth, Y.; Gough, D. O.;
Isaak, G. R.; New, R.; Rabello-Soares, M. C.
2001MNRAS.327..483H Altcode:
Measurements of both solar irradiance and p-mode oscillation
frequencies indicate that the structure of the Sun changes with
the solar cycle. Balmforth, Gough & Merryfield investigated the
effect of symmetrical thermal disturbances on the solar structure
and the resulting pulsation frequency changes. They concluded that
thermal perturbations alone cannot account for the variations in both
irradiance and p-mode frequencies, and that the presence of a magnetic
field affecting acoustical propagation is the most likely explanation
of the frequency change, in the manner suggested earlier by Gough &
Thompson and by Goldreich et al. Numerical simulations of Boussinesq
convection in a magnetic field have shown that at high Rayleigh number
the magnetic field can modify the preferred horizontal length scale
of the convective flow. Here, we investigate the effect of changing
the horizontal length scale of convective eddies on the linewidths
of the acoustic resonant mode peaks observed in helioseismic power
spectra. The turbulent fluxes in these model computations are obtained
from a time-dependent, non-local generalization of the mixing-length
formalism. The modelled variations are compared with p-mode linewidth
changes revealed by the analysis of helioseismic data collected by
the Birmingham Solar-Oscillations Network (BiSON); these low-degree
(low-l) observations cover the complete falling phase of solar activity
cycle 22. The results are also discussed in the light of observations
of solar-cycle variations of the horizontal size of granules and with
results from 2D simulations by Steffen of convective granules.
---------------------------------------------------------
Title: Effects of a gap-filling method on p-mode parameters
Authors: Fierry Fraillon, D.; Appourchaux, T.
2001MNRAS.324.1159F Altcode:
The quality of helioseismological ground-based data strongly depends
on the presence of a gap in the observational window. In order to
address that problem in the case of full-disc low-degree p-mode
velocity measurements, Fossat et al. proposed a gap-filling method
called `Repetitive music'. The autocorrelation function of the velocity
signal shows a correlation of more than 70 per cent at about 4h because
of the quasi-periodicity of p-mode peaks in the Fourier spectrum. The
method then consists of filling gaps of the velocity signal with data,
when they exist, located 4h before or after. By using Monte Carlo
simulations, we assess the effects of the gap-filling method on p-mode
parameters and their errors. A way to remove the modulation in the
power spectrum resulting from the gap-filling method is proposed; its
effects on p-mode frequencies, linewidths, amplitudes and asymmetries
are discussed as a function of frequency and signal-to-noise ratio.
---------------------------------------------------------
Title: The phenomenology of solar-cycle-induced acoustic
eigenfrequency variations: a comparative and complementary analysis
of GONG, BiSON and VIRGO/LOI data
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Isaak, G. R.;
New, R.
2001MNRAS.324..910C Altcode:
We use high-quality helioseismic data collected by three different
observational programmes during the declining phase of activity
cycle 22,Q7 and a substantial portion of the rising phase of the
current cycle (23), to study the phenomenological nature of the
cycle-induced (centroid) eigenfrequency variations. We have analysed
the frequency dependence of the shifts by fitting a power law of the
form δν<SUB>nl</SUB>~(ν<SUB>nl</SUB>)<SUP>α</SUP>/E<SUB>nl</SUB>
to the data (where the E<SUB>nl</SUB> are the mode inertias, and
α is the power-law index to be extracted). Previous studies have
suggested that a relation with α=0 provides an adequate description
of the shifts up to ν~3500μHz. However, here we show that while
nevertheless describing the shifts well up to ~2500μHz, the linear
scaling breaks down conspicuously at higher frequencies. Above this
threshold, the shifts follow a power-law dependence with α~2. Our
analyses (for 1600<=ν<=4000μHz) make use of observations made
by the ground-based GONG over the angular degree range 4<=l<=150
the ground-based BiSON over 0<=l<=2 and the VIRGO/LOI instrument
on board the ESA/NASA SOHO satellite over 0<=l<=8. We show that
GONG shifts averaged over different ranges in l, together with the BiSON
and LOI data averaged over their full quoted ranges, all scale at fixed
frequency with the normalized mode inertia ratio Q<SUB>nl</SUB>Q1. This
is to be expected if the solar-cycle perturbation affecting the modes
is confined in the surface layers; the excellent agreement also reflects
favourably on the external consistency of the different observations.
---------------------------------------------------------
Title: Observing solar-like oscillations with ELODIE spectrograph
Authors: Martić, M.; Lebrun, J. C.; Schmitt, J.; Bertaux, J. L.;
Appourchaux, T.
2001sf2a.conf..219M Altcode:
We have used ELODIE fiber-fed cross-dispersed echelle spectrograph
and the 1.93m-telescope of Observatoire de Haute Provence to obtain
precise Doppler measurements of a sample of bright stars that are
likely to undergo solar-like oscillations. Here we report the results
for Procyon from three observing runs (5, 10 and 15 nights) in Decembre
1997, Novembre 1998, and January 1999. The individual frequencies of
p-modes were searched in the interval of excess power around 1 mHz found
in the frequency spectra of each time series. The echelle diagram of
the observed and predicted p-mode frequencies from the standard model
(Chaboyer et al., 1999) for Procyon A is presented. We show also some
preliminary results for two other solar-like stars (eta Cas and z Her).
---------------------------------------------------------
Title: PICARD: solar diameter measure and g-mode search
Authors: Damé, L.; Appourchaux, T.; Berthomieu, G.; Boumier, P.;
Cugnet, D.; Gelly, B.; Provost, J.; Toutain, T.
2001ESASP.464..321D Altcode: 2001soho...10..321D
The PICARD microsatellite mission will provide 3 to 4 years simultaneous
measurements of the solar diameter, differential rotation and
solar constant to investigate the nature of their relations and
variabilities. The major instrument, SODISM, is a whole Sun imaging
telescope of Ø 110 mm which will deliver an absolute measure
(better than 4 mas) of the solar diameter and solar shape. Now in
Phase B, PICARD is expected to be launched by 2005. We recall the
scientific goals linked to the diameter measurement with emphasis on the
helioseismology g-mode interest, present the instrument optical concept
and present design, and give a brief overview of the program aspects.
---------------------------------------------------------
Title: Observing solar-like oscillations: α CMi, η Cas A and ζ
Her A
Authors: Martić, M.; Lebrun, J. C.; Schmitt, J.; Appourchaux, T.;
Bertaux, J. L.
2001ESASP.464..431M Altcode: 2001soho...10..431M
We have used ELODIE fiber-fed cross-dispersed echelle spectrograph
and the 1.93m-telescope of Observatoire de Haute Provence to obtain
precise Doppler measurements of a sample of bright stars that are
likely to undergo solar-like oscillations. Here we report the results
for Procyon from three observing runs carried out in December 1997,
November 1998, and January 1999. We show also some preliminary results
for two other solar-like stars (η Cas A and ζ Her A).
---------------------------------------------------------
Title: Does the excitation and damping of the acoustic eigenmodes
vary over the solar cycle? An insight from LOI observations
Authors: Chaplin, W. J.; Appourchaux, T.
2001ESASP.464..601C Altcode: 2001soho...10..601C
We have used observations made by the LOI instrument on board the
ESA/NASA SOHO satellite in order to try and uncover variations in
the excitation and damping of the low-angular-degree solar acoustic
eigenmodes over the solar cycle. These data were collected on the rising
phase of activity cycle 23. We have divided the dataset into independent
136-d and 1-yr time series and fitted the modes in the complex Fourier
(frequency) domain to yield estimates of the line widths and amplitudes
of the modes. The extracted parameters have then been analyzed in order
to search for solar-cycle-induced variations. Over the range 2600 <=
ν <= 3600μHz, we uncover a mean implied activity minimum-to-maximum
increase in the frequency-domain line widths of 21+/-3 per cent; a mean
decrease of 37+/-3 per cent decrease in the mode heights; and a mean
decrease of 18+/-4 per cent in the mode powers. Our analysis indicates
that - at the level of precision of the available data - the rate
at which energy is supplied to the modes remains constant (uncovered
variation 3+/-5 per cent). These results are in reasonable agreement
with recent claims by Chaplin et al. (2000) and Komm, Howe and Hill
(2000) from analyses of BiSON and GONG data respectively. Furthermore,
the signs and relative magnitudes of the extracted changes are
consistent with the speculation made by Chaplin et al. that it is
alterations in the damping, and not the forcing, of the modes that
gives rise to the variations observed over the solar activity cycle.
---------------------------------------------------------
Title: Effects of a gap filling method on p-mode parameters
Authors: Fierry Fraillon, D.; Appourchaux, T.
2001ESASP.464..347F Altcode: 2001soho...10..347F
The quality of helioseismological ground based data strongly depends
on the presence of gap in the observational window. In order to
address that problem in the case of full disk low p-mode velocity
measurements, Fossat et al. (1999) proposed a gap filling method called
"Repetitive music". The autocorrelation function of the velocity
signal shows a correlation of more than 70% at about 4 hours due to
the quasi-periodicity of p-mode peaks in the Fourier spectrum. The
method then consists in filling gaps of the velocity signal by data,
when they exist, located 4 hours before or after. By using Monte Carlo
simulations we assess the effects of the gap filling method on p-mode
parameters and their errors. A way to remove the modulation, resulting
from the gap-filling method, in the power spectrum is proposed; its
effects on p-mode frequencies, linewidths, amplitudes and asymmetries
are discussed as a function of both frequency and signal-to-noise
ratio of the observational data.
---------------------------------------------------------
Title: Results from the luminosity oscillations imager on board SOHO:
low-degree p-mode parameters for a 4-year data set
Authors: Appourchaux, T.
2001ESASP.464...71A Altcode: 2001soho...10...71A
I report on the results from a 4-year VIRGO/LOI data set. I have
analysed independently four 1-year time series mainly for minimizing
the effect of solar activity. For l<=3 the p-mode data are fitted
using the Fourier spectra taking into account the mode leakage and noise
correlations. For l>=4, the data are fitted using simultaneously the
power spectra of l=4.7, l=5.8 and l=1.6. The effect of solar activity
upon frequencies, linewidths, mode amplitude, energy rate, asymmetry
and splitting is studied. Most of these results in intensity confirms
earlier measurements made in velocity.
---------------------------------------------------------
Title: Probing the solar cycle: a comparative and complementary
analysis of GONG BiSON and VIRGO/LOI eigenfrequency shifts
Authors: Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; New, R.;
Appourchaux, T.
2001ESASP.464...83C Altcode: 2001soho...10...83C
We use high-quality helioseismic data collected by GONG (over 4 <=
l <= 140), BiSON (0 <= l <= 2) and VIRGO/LOI (0 <= l <=
8) to study the phenomenological nature of the cycle-induced (centroid)
eigenfrequency variations. We have analyzed the frequency dependence
of the shifts by fitting a power-law of the form δν<SUB>nl</SUB> ~
(ν<SUB>nl</SUB>)<SUP>α</SUP>/E<SUB>nl</SUB> to the data (where the
E<SUB>nl</SUB> are the mode inertias, and α is the power-law index to
be extracted). Previous studies have suggested that a relation with
α = 0 provides an adequate description of the shifts up to ν ≍
3500 μHz. However, here we show that while nevertheless describing
the shifts well up to ~2500 μHz, the linear scaling breaks down
conspicuously at higher frequencies. Above this threshold, the shifts
follow a power-law dependence with α ~ 2. We also ahow that GONG
shifts, averaged over different ranges in l together with the BiSON
and LOI data averaged over their full quoted ranges, all scale at
fixed frequency with the normalized mode inertia ratio Q<SUB>nl</SUB>
(Christensen-Dalsgaard & Berthomieu 1991). This is to be expected
if the solar-cycle perturbation affecting the modes is confined in
the surface layers; the excellent agreement also reflects favourably
on the external consistency of the different observations.
---------------------------------------------------------
Title: Dependence on azimuthal order of the amplitudes of low-degree
p modes
Authors: Fröhlich, C.; Appourchaux, T.; Gough, D. O.
2001ESASP.464..629F Altcode: 2001soho...10..629F
The m-dependence of the amplitudes of the multiplets of low-degree p
modes contains information about the latitudinal distribution of the
power in the excitation of the oscillations. We present estimates of
those amplitudes from 4 years of VIRGO/LOI observations. Variation of
the excitation with magnetic activity is studied.
---------------------------------------------------------
Title: g-mode detection: Where do we stand?
Authors: Appourchaux, T.; Andersen, B.; Berthomieu, G.; Chaplin, W.;
Elsworth, Y.; Finsterle, W.; Frölich, C.; Gough, D. O.; Hoeksema,
T.; Isaak, G.; Kosovichev, A.; Provost, J.; Scherrer, P.; Sekii, T.;
Toutain, T.
2001ESASP.464..467A Altcode: 2001soho...10..467A
We review the recent developments in determining the upper limits to
g-mode amplitudes obtained by SOHO instruments, GONG and BiSON. We
address how this limit can be improved by way of new helioseismic
instruments and/or new collaborations, hopefully providing in the not
too distant future unambiguous g-mode detection.
---------------------------------------------------------
Title: On measuring low-degree p-mode frequency splitting with
full-disc integrated data
Authors: Appourchaux, T.; Chang, H. -Y.; Gough, D. O.; Sekii, T.
2000MNRAS.319..365A Altcode:
The standard method of measuring rotational splitting from solar
full-disc oscillation data, based on maximum-likelihood fitting of
multi-Lorentzian profiles to oscillation power spectra, systematically
overestimates the splitting. One of the reasons is that the maximum
likelihood estimators (MLE) become unbiased only asymptotically as
the number of data tends to infinity; for a finite data set they
are often biased, inducing a systematic error. In this paper we
assess by Monte Carlo simulations the amount of systematic error
in the splitting measurement, using artificially generated power
spectra. The simulations are carried out for multiplets of degree
S(t) = Σ<SUB>k</SUB>S<SUB>k</SUB>(t), l=1, 2 and 3 with various
signal-to-noise ratios, linewidths and observing times. We address
the possible use of non-MLE estimators that could provide a smaller
or negligible systematic error. The implication for asteroseismology
is also discussed.
---------------------------------------------------------
Title: Observational Upper Limits to Low-Degree Solar g-Modes
Authors: Appourchaux, T.; Fröhlich, C.; Andersen, B.; Berthomieu, G.;
Chaplin, W. J.; Elsworth, Y.; Finsterle, W.; Gough, D. O.; Hoeksema,
J. T.; Isaak, G. R.; Kosovichev, A. G.; Provost, J.; Scherrer, P. H.;
Sekii, T.; Toutain, T.
2000ApJ...538..401A Altcode:
Observations made by the Michelson Doppler Imager (MDI) and Variability
of solar IRradiance and Gravity Oscillations (VIRGO) on the Solar and
Heliospheric Observatory (SOHO) and by the ground-based Birmingham
Solar Oscillations Network (BiSON) and Global Oscillations Network
Group (GONG) have been used in a concerted effort to search for solar
gravity oscillations. All spectra are dominated by solar noise in the
frequency region from 100 to 1000 μHz, where g-modes are expected to be
found. Several methods have been used in an effort to extract any g-mode
signal present. These include (1) the correlation of data-both full-disk
and imaged (with different spatial-mask properties)-collected over
different time intervals from the same instrument, (2) the correlation
of near-contemporaneous data from different instruments, and (3) the
extraction-through the application of complex filtering techniques-of
the coherent part of data collected at different heights in the solar
atmosphere. The detection limit is set by the loss of coherence
caused by the temporal evolution and the motion (e.g., rotation)
of superficial structures. Although we cannot identify any g-mode
signature, we have nevertheless set a firm upper limit to the amplitudes
of the modes: at 200 μHz, they are below 10 mm s<SUP>-1</SUP> in
velocity, and below 0.5 parts per million in intensity. The velocity
limit corresponds very approximately to a peak-to-peak vertical
displacement of δR/R<SUB>solar</SUB>=2.3×10<SUP>-8</SUP> at the
solar surface. These levels which are much lower than prior claims,
are consistent with theoretical predictions.
---------------------------------------------------------
Title: Source of excitation of low-l solar p modes: characteristics
and solar-cycle variations
Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; Isaak, G. R.;
Miller, B. A.; New, R.
2000MNRAS.314...75C Altcode:
We investigate various properties of the excitation source that
is responsible for driving the acoustic p-mode oscillations of the
Sun. Current prejudice places this in the superadiabatic layer of
the convection zone. We consider in detail how the precise nature of
the resonant mode spectrum is modified: (i) as a result of the impact
of different source-multipole mixtures; and (ii) as a function of the
radial extent of the source. To do this, we model the observed resonant
spectra with the solutions to a simple, one-dimensional wave equation
which is intended to describe the essential elements of the solar
resonant acoustic cavity. Further, we also fit these models to the
low-l peaks in a high-resolution power spectrum generated from data
collected by the Birmingham Solar-Oscillations Network (BiSON). We
also use the extensive BiSON data set to search for variations in the
source characteristics over the solar cycle.
---------------------------------------------------------
Title: COROT -- A Unique Database for Low Amplitude Variability
Between 1 Minute and 150 Days
Authors: Michel, E.; Baglin, A.; Barge, P.; Catala, C.; Auvergne,
M.; Weiss, W. W.; Appourchaux, T.; Garrido, R.; COROT Team
2000ASPC..203...69M Altcode: 2000ilss.conf...69M; 2000IAUCo.176...69M
COROT is a high precision wide field photometry experiment from space,
funded in the framework of the CNES “Petites Missions” program
(the PI is A. Baglin). It will observe approximately 30000 objects
with m<SUB>V</SUB> between 4.5 and 15.5 over long observational
periods (up to 150 d), with a time sampling between 1 s and 16 min,
a precision of the order of 10<SUP>-4</SUP> per measurement. The
scientific objectives are stellar seismology and the search for
telluric planets. The instrument and the core program have already
been presented in several places. We here focus on a description of the
characteristics of the data to be obtained with COROT. The large amount
of high quality data collected by COROT will constitute rich material
for several research programs beyond the core program as already defined
(http://www.astrsp-mrs.fr/www/corot.html). A call for proposal of
additional programs will be made during Northern Spring 2000.
---------------------------------------------------------
Title: I-V phase difference and gain analysis of GONG full-disk data
Authors: Oliviero, M.; Severino, G.; Straus, T.; Jefferies, S. M.;
Appourchaux, T.
2000MmSAI..71..999O Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Depth of excitation and reversal of asymmetry of low-l
solar P modes: a complementary analysis of BiSON<SUP>*</SUP> and
VIRGO/SPM† data
Authors: Chaplin, W. J.; Appourchaux, T.
1999MNRAS.309..761C Altcode:
We use the solutions to a simple, one-dimensional wave equation -
which is intended to describe the essential elements of the solar
resonant acoustic cavity - as formalistic models to which to fit
low-l modes in observational helioseismic power spectra. We have
analysed data collected in velocity, by the ground-based Birmingham
Solar-Oscillations Network (BiSON), and in intensity, by the full-disc
VIRGO Sun photometers (SPM) on board the ESA/NASA SOHO satellite. Our
analysis extracts, as a function of the modal radial overtone number
n, direct estimates of: the location of the excitation source of the
acoustic resonances; and the size of the component of the convective
granulation that is correlated to the observations of the resonances,
and is responsible for the reversal of asymmetry of the mode profiles
when different observation techniques are applied (i.e. intensity
or Doppler velocity measurements). This information is coded in the
complicated forms of the observed, resonant profiles.
---------------------------------------------------------
Title: Evidence for global pressure oscillations on Procyon
Authors: Martić, M.; Schmitt, J.; Lebrun, J. -C.; Barban, C.; Connes,
P.; Bouchy, F.; Michel, E.; Baglin, A.; Appourchaux, T.; Bertaux,
J. -L.
1999A&A...351..993M Altcode:
Precise Doppler measurements of the star Procyon (alpha CMi, HR
2943) have been obtained with the ELODIE fiber-fed cross-dispersed
echelle spectrograph on the 1.93 m telescope at Observatoire de Haute
Provence. Here, we present the analysis of data from 10 days observing
run carried out in November 1998. We detect significant excess in
the power between 0.5-1.5 mHz in the periodograms of the time series
of mean Doppler shifts. Observations of eta Cas made with the same
instrument during the same time interval and in almost identical
night conditions show a flat spectrum in this frequency range,
indicating that the excess of Doppler signal seen on Procyon is of
stellar origin. When data from the whole run are jointly analyzed,
a period analysis places an upper limit of 0.50-0.60 ms<SUP>-1</SUP>
for the amplitude of oscillations, while the frequency cutoff is around
1.5 mHz. The power evidently drops near 0.55 and 1.5 mHz on the average
of unfiltered power spectra of individual nights, which is consistent
with the expected p-mode oscillation properties for Procyon. Several
equispaced peaks in frequency are recurrent in the power spectra of two
independent segments of 4 and 3 contiguous nights; the most probable
frequency spacing seems to be 55 mu Hz. In conclusion, we now have an
instrument set-up which is sufficiently stable and fast to be used for
a multi-site campaign involving instruments with comparable velocity
precisions, to detect the oscillation modes of sun-like stars. Based
on observations obtained at the Observatoire de Haute-Provence (CNRS,
France)
---------------------------------------------------------
Title: Solar low-degree p-mode parameters from the GONG network
Authors: Rabello-Soares, M. C.; Appourchaux, T.
1999A&A...345.1027R Altcode:
Low-degree solar p modes observed by the GONG network have been analysed
for l <= 6, yielding accurate measurements of their frequencies,
splittings and linewidths. The results obtained here show significant
improvement on previous determinations, especially for increasing the
number of identified modes with l <= 3 and for minimizing the bias
on the splitting determination and the error bars. A more realistic
approach was used to fit the helioseismic data assuming that the
observed spectra are statistically dependent upon one another. This
is in contrast to what is commonly done and the result is a better
treatment of the leakage between the modes. Moreover, the effect of
an imperfect knowledge of the leakage within the elements of the l=1
multiplets upon their splitting determination is analysed. In addition,
the effect of the leakage between the modes of different degrees
upon the p-mode parameters determination is shown, and a procedure
for `cleaning' the spatial alias is described leading to splitting
coefficients with smaller systematic errors than before.
---------------------------------------------------------
Title: Space and Time Analysis of the Solar Photospheric Dynamics
at Moderate-l Values
Authors: Oliviero, M.; Severino, G.; Straus, Th.; Jefferies, S. M.;
Appourchaux, T.
1999ApJ...516L..45O Altcode:
A space-time analysis of 36 days' worth of full-disk intensity and
velocity images, obtained by the Global Oscillation Network Group,
is used to produce a high-resolution l-ν phase-difference spectrum
for the spectral range (4<=l<=2000, 0<=ν<=8.3 mHz). This
is the first time a phase-difference spectrum has been produced for
intermediate-l values. The phase differences on the p-mode ridges
are found to linearly increase from ~65° at 2 mHz up to ~95°
at 4.7 mHz. Only near 3.9 mHz are the differences close to 90°,
the theoretically expected phase for adiabatic evanescent waves. The
phases between the ridges exhibit a steplike behavior in frequency with
negative values at low frequency and positive values (greater than 90°)
at high frequency. The negative phase values are consistent with the
extension to low- and moderate-l values of the plateau-interridge regime
discovered by Deubner et al. in 1990. However, positive phase values,
which represent higher phase for the solar background than for the
acoustic modes, were not expected. An understanding of this observed
phase-difference behavior will improve our knowledge of the nature of
the solar background and its interaction with the acoustic p-modes.
---------------------------------------------------------
Title: PICARD: simultaneous measurements of the solar diameter,
differential rotation, solar constant and their variations
Authors: Damé, Luc; Hersé, Michel; Thuillier, Gérard; Appourchaux,
Thierry; Crommelynck, Dominique; Dewitte, Steven; Joukoff, Alexandre;
Fröhlich, Claus; Laclare, Francis; Delmas, Christian; Boumier, Patrick
1999AdSpR..24..205D Altcode:
PICARD is a CNES micro-satellite mission due for flight by the end
of 2002, named after the name of a French astronomer who first
observed with consistency the solar diameter changes during the
Maunder minimum in the 16th century. It consists of two instruments
measuring (i) the solar diameter and differential rotation, and (ii)
the total solar irradiance. These quantities are fundamental for the
understanding of the solar-Terrestrial relations, e.g. the influence
of the Sun on the Earth's climate, and of the internal structure
of the Sun. The continuous - or nearly continuous - viewing of the
Sun from an appropriate orbit, the 5 minutes sampling rate and the
very low noise measurements, will allow g-modes detection and precise
diameter measurements besides accurately establishing the relationship
between irradiance and diameter changes. Providing an absolute measure
of the solar diameter to 1 milliarcsecond, PICARD is the first step
towards instruments capable of accurate and perennial measurements,
for the centuries to come, of the solar-terrestrial influence. The
objectives of the mission, instrument capabilities, observing modes
and performances are described.
---------------------------------------------------------
Title: The art of fitting p-mode spectra. II. Leakage and noise
covariance matrices
Authors: Appourchaux, T.; Rabello-Soares, M. -C.; Gizon, L.
1998A&AS..132..121A Altcode: 1997astro.ph.10131A
In Part I we have developed a theory for fitting p-mode Fourier spectra
assuming that these spectra have a multi-normal distribution. We showed,
using Monte-Carlo simulations, how one can obtain p-mode parameters
using “Maximum Likelihood Estimators". In this article, hereafter
Part II, we show how to use the theory developed in Part I for fitting
real data. We introduce 4 new diagnostics in helioseismology: the
(m,nu ) echelle diagram, the cross echelle diagram, the inter echelle
diagram, and the cross spectrum ratio. These diagnostics are extremely
powerful to visualize and understand the covariance matrices of the
Fourier spectra, and also to find bugs in the data analysis code. The
diagrams are used to verify the computation of the leakage matrices,
and also to measure quantitatively these matrices. Cross spectrum ratios
are used to obtain quantitative information on the noise covariance
matrices. Numerous examples using the LOI/SOHO and GONG data are given.
---------------------------------------------------------
Title: The art of fitting p-mode spectra. I. Maximum likelihood
estimation
Authors: Appourchaux, T.; Gizon, L.; Rabello-Soares, M. -C.
1998A&AS..132..107A Altcode: 1997astro.ph.10082A
In this article we present our state of the art of fitting helioseismic
p-mode spectra. We give a step by step recipe for fitting the spectra:
statistics of the spectra both for spatially unresolved and resolved
data, the use of Maximum Likelihood estimates, the statistics of
the p-mode parameters, the use of Monte-Carlo simulation and the
significance of fitted parameters. The recipe is applied to synthetic
low-resolution data, similar to those of the LOI, using Monte-Carlo
simulations. For such spatially resolved data, the statistics of the
Fourier spectrum is assumed to be a multi-normal distribution; the
statistics of the power spectrum is not a chi (2) with 2 degrees of
freedom. Results for l=1 shows that all parameters describing the p
modes can be obtained with negligible bias and with minimum variance
provided that the leakage matrix is known. Systematic errors due to
an imperfect knowledge of the leakage matrix are derived for all the
p-mode parameters.
---------------------------------------------------------
Title: Asymmetry and Frequencies of Low-Degree p-Modes and the
Structure of the Sun's Core
Authors: Toutain, T.; Appourchaux, T.; Fröhlich, C.; Kosovichev,
A. G.; Nigam, R.; Scherrer, P. H.
1998ApJ...506L.147T Altcode:
An accurate determination of the frequencies of low-degree solar
p-modes is an important task of helioseismology. Using 679 days of
solar oscillation data observed in Doppler velocity and continuum
intensity from two Solar and Heliospheric Observatory instruments
(the Michelson Doppler Imager and the SunPhotoMeter), we show that
fitting the spectra with Lorentzian profiles leads to systematic
differences between intensity and velocity frequencies as large as
0.1 μHz for angular degrees l=0, 1, and 2 because of the opposite
asymmetry between intensity and velocity. We use a physics-based
asymmetrical line shape to fit p-mode lines, and we demonstrate
that their asymmetry is statistically significant and that frequency
differences are considerably reduced. These measurements provide more
accurate estimates of the solar eigenfrequencies. We discuss inferences
of the structure of the solar core.
---------------------------------------------------------
Title: Results from the Luminosity Oscillations Imager on board SOHO:
Low-degree p-mode Parameters for a 2-year Data Set
Authors: Appourchaux, T.; Virgo Team
1998ESASP.418...99A Altcode: 1998soho....6...99A
I will report on the results from a 2-year LOI time series starting on
March 27, 1995 and ending on March 26, 1998. From the data set, I have
analysed independently two 1-year time series mainly for minimizing
the effect of solar activity. For l < 3 the p-mode data are fitted
using the Fourier spectra taking into account the mode leakage and
noise correlations (Appourchaux et al, 1998; Schou, 1992). For 4 <
l < 9, the small number of pixels (12) lead to undersampling that
result into non-inversible leakage matrices: the Fourier spectra cannot
be utilised anymore (Appourchaux et al, 1998). In addition for these
degrees, the spectra of the l = 4,5 modes are strongly polluted by the
l = 7,8 modes, and vice versa. Due to these two major problems, I have
fitted simultaneously the power spectra of l = 4,7 and l = 5,8; this is
clearly an approximation that will lead to systematic errors. I will
give tables of frequencies, splittings and linewidths for the 2-year
data set. The splittings are compared with other data sets such as LOWL,
MDI and GONG. The effects of the solar activity is also studied.
---------------------------------------------------------
Title: The art of fitting p-mode spectra
Authors: Appourchaux, T.; Gizon, L.
1998IAUS..185...43A Altcode:
We describe how to extract the p-mode parameters from complex Fourier
spectra using maximum likelihood estimators. We expect our description
to be quite general and didactic. We discuss problems such as the
choice of the optimal filters and the construction of the leakage and
covariance matrices. The LOI/SOHO Team makes use of these methods.
---------------------------------------------------------
Title: Sources of Amplitude Modulation of Solar P-Modes
Authors: Leifsen, Torben; Andersen, Bo; Appourchaux, Thierry
1998ESASP.418..939L Altcode: 1998soho....6..939L
We study the amplitude variation with time of the solar radial
p-modes. Continuous datasets from more than two years of observations
with the SOHO/VIRGO SPM and LOI instruments were used. A Hilbert
transform method was used to study the time variation of the amplitudes
of the l = 0-3 modes with radial order 12-32. The observed amplitudes of
the modes vary substantially with time on a large range of timescales
up to more than a solar rotation. As expected the power spectra of
the amplitude variation show little or no consistent periodicities for
most of the modes. However, for some of the modes, specifically for it
l = 0, n = 21 and 22, a strong modulation is observed with the solar
sidereal rotation frequency. This is a very surprising result as the
{l} = 0 modes should be insensitive to the solar rotation. In contrast
the SPM blue channel irradiance observations show a modulation with
the solar synodic rotation frequency. This is as one would expect as
active regions rotate over the solar disc and thereby modulate the
irradiance signal. A comparison with MDI velocity data show that the
amplitude modulation of the modes closely resembles the modulation as
observed with VIRGO/SPM. This shows that the observed modulation is
not an effect of the irradiance variation due to active regions, but
rather a modulation of the mode itself by rotation. This conclusion is
strengthened by the fact that the symmetric {l} = 0 modes are modulated
by the sidereal and not the synodic rotation frequency. The two years
of observations cover times of both low and higher solar activity as
the activity of the new solar cycle started in the summer of 1997. In
the solar irradiance one can see the onset of the new solar cycle
as a frequency shift to lower frequencies as the activity appear at
higher solar latitudes. Surprisingly a similar shift is also seen in
the modulation of the two modes, indicating that the modulation of
the modes is closely connected to the latitudes of solar activity.
---------------------------------------------------------
Title: Line Asymmetry of VIRGO and MDI Low-Degree p Modes
Authors: Toutain, T.; Appourchaux, T.; Frohlich, C.; Kosovichev, A.;
Rakesh, N.; Scherrer, P.
1998ESASP.418..973T Altcode: 1998soho....6..973T
Using continuous time series of 610 days of velocity (MDI, LOI-proxy)
and intensity (VIRGO, SPM and LOI) we show that Lorentzian profiles as
a model of low-degree p-mode line leads to systematic differences in
the determination of intensity and velocity mode frequencies. These
differences, as large as 0.1 muHz for degrees l = 0, 1, 2 and 3,
are frequency-dependent. The use of a physics-based asymmetrical line
shape (Rakesh et al., 1998) to fit the same lines has allowed us to
significantly reduce differences in the frequency determination. P-mode
lines in velocity exhibit a significant negative asymmetry (excess
of power in the left wing) whereas p-modes lines in intensity have a
positive asymmetry (excess of power in the right wing). The magnitude
and sign of this asymmetry are directly related to the location of
the source of p-mode excitation and to the correlation between mode
and solar noise.
---------------------------------------------------------
Title: Rotation of the Solar Core Inferred from GONG Data
Authors: Rabello-Soares, M. C.; Appourchaux, T.; Christensen-Dalsgaard,
J.
1998ESASP.418..837R Altcode: 1998soho....6..837R
We present inferences of the solar core rotation derived from GONG
frequency splittings. The GONG data for the low-degree modes (l <=
6) are for the one year period Aug. 1995-1996; these splittings
were determined using a new method of fitting heliosismic spectra
(Rabello-Soares & Appourchaux 1998). These are combined with
GONG data for higher degree modes, as obtained by the GONG team (Hill
et al. 1996). We have employed a new two-dimensional implementation
of the optimally localized averages (OLA) inversion method (Chaplin
et al. 1998). As in one dimension, the OLA produces better-localized
averaging kernels than do least-squares techniques. This is particularly
beneficial in the deep interior, where it is in any case difficult to
obtain localized information.
---------------------------------------------------------
Title: Time Dependence of Solar Noise Observed with VIRGO
Authors: Andersen, Bo; Leifsen, Torben; Appourchaux, Thierry; Frohlich,
Claus; Jiménez, Antonio; Wehrli, Christoph
1998ESASP.418...83A Altcode: 1998soho....6...83A
The effect of non- and quasiperiodic solar surface structures dominate
the power spectra of solar irradiance and radiance over a broad range
of time scales. Only in the p-mode region above about 2 mHz and in the
rotationally dominated region below about 3 μ Hz there seems to be
narrow stationary peaks. The solar background signal, or solar noise has
clear large scale quasi-stationary structures that seems to be closely
correlated to the combination of timescales and contrasts of the solar
surface sources. The dominant sources are the solar granulation and
supergranulation. The solar noise determines the detection limit in
the search for g-modes. Thus an increased understanding of it may be
helpfull in this search. In addition this understanding will be usefull
to determine the properities of stellar small scale surface structures
from the data from future asteroseismology space missions. In this
study we use the VIRGO data to study the time variation of the solar
noise with timescales from about one day to about one year.
---------------------------------------------------------
Title: Statistical Properties of the Amplitude Modulation of Solar
p-Modes
Authors: Andersen, Bo; Aarset, Magne; Leifsen, Torben; Appourchaux,
Thierry; Frohlich, Claus; Hoeksema, J. T.; Jiménez, Antonio; Toutain,
Thierry
1998ESASP.418..897A Altcode: 1998soho....6..897A
The low degree solar p-modes show amplitude modulation at all observable
timescales. For some modes a large fraction of this modulation seems
to be correlated to the solar rotation. For other modes there seems
to be little or no deterministic component in the modulation. Only
intermittent correlation between the modulation of different modes
have been observed. This is to be expected if the excitation of modes
is completely stochastic. None of the observational methods observe the
modes directly. In different ways they all observe the solar atmospheres
response to the modes. This implies that the modes may be modulated by
this response. By studying the statistical properties of the different
observed modes we attempt to discriminate between variations in the
modes themselves and the atmospheric response. In this work we study the
statistical properties of the mode amplitude variations for radial order
p-modes observed with the VIRGO and SOI/MDI instruments on SOHO. The
time scales studied span the region from 0.2 μ Hz to 15 muHz. Here,
we are modelling the amplitude modulation, utilising the concepts of
state space models, as a stochastic process and study the properties
of this model as function of radial order and line width of the modes.
---------------------------------------------------------
Title: Observations of the latitudinal variation of the solar radiance
of non-active regions of the sun.
Authors: Domingo, V.; Sanchez, L.; Appourchaux, T.; Andersen, B.
1998IAUS..185..111D Altcode:
The Luminosity Oscillations Imager (LOI) of the VIRGO experiment
aboard SOHO provides continuous measurement of the solar irradiance
in a 5 nm band around 500 nm. The solar image is broken down in 12
pixels distributed in 4 latitudinal bands. The first year of operation
of the instrument has taken place during a period of solar minimum
activity. The measurements provide an indication of the distribution
of the solar irradiance variations versus latitude. Contributions to
the observed variations due to the presence of active regions are
discussed in relation to the possible effect of the evolving solar
cycle (structure of the convection zone): short term variations versus
long term variations. The problem of the photometric stability of
the measurements needed for the investigation is thoroughly treated
by self consistency and by comparison with other instruments on SOHO
(VIRGO sun- photometers and MDI intensity measurements).
---------------------------------------------------------
Title: LOI low-degree rotational splittings
Authors: Appourchaux, T.; Rabello Soares, M. C.; Gizon, L.
1998IAUS..185..167A Altcode:
We present measurements of rotational splitting frequencies of
low-degree p-modes. The data which have been analyzed correspond to
one-year spatially resolved observations obtained with the Luminosity
Oscillation Imager onboard the SOHO spacecraft.
---------------------------------------------------------
Title: Observational Upper Limits for Low-Degree Solar g-modes
Authors: Fröhlich, C.; Finsterle, W.; Andersen, B.; Appourchaux, T.;
Chaplin, W. J.; Elsworth, Y.; D. O. Gough; Hoeksema, J. T.; Isaak,
G. R.; Kosovichev, A. G.; Provost, J.; Scherrer, P. H.; Sekii, T.;
Toutain, T.
1998ESASP.418...67F Altcode: 1998soho....6...67F
No abstract at ADS
---------------------------------------------------------
Title: Amplitude modulation of radial p-modes from Virgo
Authors: Leifsen, T.; Andersen, B. N.; Appourchaux, T.; Frohlich,
C.; Jimenez, A.; Toutain, T.; Wehrli, C.
1998IAUS..185..113L Altcode:
We present results from wavelet analysis of more than one year of
data from the VIRGO Sun Photometers (SPM) and the VIRGO Luminosity
Oscillation Imager (LOI) onboard the SOHO spacecraft. The temporal
behaviour of p-modes with l=0--2 is presented. The analysis of
the l=0 modes show a modulation of the mode amplitudes with the
solar rotation. This result is quite surprising as the l=0 modes
should not be sensitive to the solar rotation. Possible effects of
varying solar activity on the modulation of the mode amplitudes is
investigated. The effect of the modulation on the fitting of mode lines
and determination of the mode frequencies is also studied. Wavelet
analysis has a fundamental limitation in the ability to achieve
simultaneous high frequency and time resolution. In order to be able
to study the rotationally split components of the l=1 modes with good
time resolution, we apply a spatial filtering technique on the LOI
data to separate the different components.
---------------------------------------------------------
Title: A comparison of low-degree solar p-mode frquencies from BISON
and LOI
Authors: Appourchaux, T.; Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.;
McLeod, C. P.; Miller, B. A.; New, R.
1998IAUS..185...45A Altcode:
Here, we compare the low-degree solar p-mode frequencies returned from
the analysis of two, contemporaneous, independent helioseismological
data sets collected during 1996. The first comprises Doppler velocity
observations of the 770-nm line of potassium, made in integrated
sunlight by the six-station, terrestrial Birmingham Solar-Oscillations
Network (BiSON). The second consists of irradiance distribution
measurements of the solar disc, made at 500rm nm, by the Luminosity
Oscillations Imager (LOI), which is part of the VIRGO experiment on
the ESA/NASA SOHO satellite.
---------------------------------------------------------
Title: LOI/SOHO constraints on oblique rotation of the solar core
Authors: Gizon, L.; Appourchaux, T.; Gough, D. O.
1998IAUS..185...37G Altcode:
The Sun is usually assumed to rotate about a single axis, tilted with
respect to the ecliptic normal by an angle of 7.25 degrees. Although
we have an excellent knowledge of the direction of the rotation axis of
the photospheric layers, we cannot exclude a priori that the direction
of the rotation axis could vary as a function of radius. We have tried
to check whether the assumption of rotation about a unique axis is
consistent with helioseismic data. We report on an attempt to measure
the directions of the pulsation axes of several low-degree modes of
oscillation in the LOI/SOHO Fourier spectra.
---------------------------------------------------------
Title: The Structure of the Solar Core: an Observer's Point of View
Authors: Appourchaux, T.
1998ESASP.418...37A Altcode: 1998soho....6...37A
Since the beginning of helioseismology, most of the internal and
dynamics structure of the Sun has been revealed or so we thought. The
last island where our powerful tools start to fail is the solar core,
where nuclear reactions take place. With the advent of SOHO and GONG,
we have now a quality of helioseismic data without precedence that
should enable us to understand better the physics of the deepest solar
regions. This goal can be partially achieved by measuring low-degree
rotational splitting of p-modes, and by detecting the elusive
g-modes. In a first part, I will review the fitting techniques that
are being used for inferring the rotational splittings of low-degree
p-modes. I will particularly focus on Fourier spectra fitting developped
by Schou (1992) and refined by Appourchaux et al (1998). I will show
how one can visualize from the data, the leakage matrix and how one
can clean the data from the mode leakages. I will give examples of
systematic errors introduced by the leakage matrix and by modes of
aliasing degrees. I will also compare the Fourier spectra fitting
technique to others techniques that use power spectra. I will give some
recent results from SOHO and GONG. In a second part, I will report on
the progress of the Phoebus group for detecting g-modes. The Phoebus
group is composed of team members of BiSON, VIRGO and SOI/MDI. I will
summarize some of the techniques we used for finding g-modes, and how
one can use those for finding low-order low-frequency p-modes. I will,
most probably, not report on g-mode detection but most likely stress
that the future ahead of us is brighter than ever.
---------------------------------------------------------
Title: Comparative Studies of Low-Order and Low-Degree Solar p Modes
Authors: Appourchaux, T.; Andersen, B.; Chaplin, W.; Elsworth, Y.;
Finsterle, W.; Frohlich, C.; Gough, D.; Hoeksema, J. T.; Isaak, G.;
Kosovichev, A.; Provost, J.; Scherrer, P.; Sekii, T.; Toutain, T.
1998ESASP.418...95A Altcode: 1998soho....6...95A
The amplitudes of solar p-modes decrease steeply with decreasing
radial order below about 17. The background solar signal (solar noise)
in general increases steadily with decreasing frequency. For the
irradiance and radiance measurements with VIRGO or SOI/MDI on SOHO this
combination makes it difficult to detect low degree modes below about
1.8 mHz. The solar noise as observed in velocity with SOI/MDI or the
ground based BISON network is significantly lower in this region than
in intensity measurements. This allows low degree modes to be observed
close to 1 mHz. We present results of detection and charaterization
of the lowest order observable p-modes both in velocity and intensity
measurements. Where applicable the properties of the modes observed
with the two methods are compared.
---------------------------------------------------------
Title: The Effect of Amplitude Modulation on Asymmetries of Solar
p-Modes
Authors: Andersen, Bo; Leifsen, Torben; Appourchaux, Thierry; Frohlich,
Claus; Hoeksema, J. T.; Toutain, Thierry
1998ESASP.418..893A Altcode: 1998soho....6..893A
The low degree solar p-modes show an asymmetry in their line profiles
that both depend on the observational technique and on the radial
order of the modes. Typically the modes determined from observations
with Doppler shift methods show an asymmetry towards lower frequency
while the opposite is the case for modes determined from irradiance and
radiance observations. The difference in asymmetry is probably caused by
near surface effects. If the modes are fitted with symmetric functions
this leads to a systematic shift in the frequency determinations for
the two data sets. This may lead to systematic differences in the
inversions based on the different frequencies. All the mode amplitudes
show significant time variation. The typical centroid frequency also
varies with timescales from a few days to the solar cycle. These
variations may set absolute limits to the observable accuracy of the
frequency determination. These time modulations may influence the
observed line profiles and thus the frequency determinations. Here we
present results of the effect on the mode asymmetry of the amplitude
modulation of low degree modes observed with VIRGO and SOI/MDI. The
range in timescales is from a few days to a few solar rotations.
---------------------------------------------------------
Title: Measurement of GONG Low-Degree p-Mode Parameters
Authors: Rabello-Soares, M. C.; Appourchaux, T.
1998ESASP.418..299R Altcode: 1998soho....6..299R
Low-degree solar p modes observed by the GONG network have been analysed
for ell <= 6 yielding accurate measurements of their frequencies,
splittings and linewidths. The results obtained show significant
improvement over the GONG project parameters especially for minimizing
the bias on the splitting and the error bars. We used a new method
of fitting helioseismic spectra where, instead of fitting the power
spectra, we fitted the Fourier spectra involving the knowledge of the
mode leakage matrix. The effect of an imperfect knowledge of the ell =
1 leakage matrix upon the splitting determination is shown both for
power spectra and Fourier spectra fitting. In addition, the effect of
the leakage between the modes of different degrees, or spatial alias,
upon the splitting coefficient is analysed. A procedure for cleaning
the spatial alias is described leading to splitting coefficients with
smaller systematic errors than before.
---------------------------------------------------------
Title: On the Effect of Active Regions on the Solar Irradiance
Authors: Domingo, V.; Sanchez, L.; Appourchaux, T.; Fröhlich, C.;
Wehrli, C.; Crommelynck, D.; Pap, J.
1997ESASP.415..469D Altcode: 1997cpsh.conf..469D
No abstract at ADS
---------------------------------------------------------
Title: Successful Recovery from LOI Cover In-Orbit Anomaly on SOHO
Authors: Yorck, M.; Appourchaux, T.; Eiden, M.
1997ESASP.410..215Y Altcode: 1997smt..conf..215Y
No abstract at ADS
---------------------------------------------------------
Title: Tri-Phonic Helioseismology: Comparison of Solar P Modes
Observed by the Helioseismology Instruments Aboard SOHO
Authors: Toutain, T.; Appourchaux, T.; Baudin, F.; Fröhlich, C.;
Gabriel, A.; Scherrer, P.; Andersen, B. N.; Bogart, R.; Bush, R.;
Finsterle, W.; García, R. A.; Grec, G.; Henney, C. J.; Hoeksema,
J. T.; Jiménez, A.; Kosovichev, A.; Roca Cortés, T.; Turck-Chièze,
S.; Ulrich, R.; Wehrli, C.
1997SoPh..175..311T Altcode:
The three helioseismology instruments aboard SOHO observe solar p modes
in velocity (GOLF and MDI) and in intensity (VIRGO and MDI). Time series
of two months duration are compared and confirm that the instruments
indeed observe the same Sun to a high degree of precision. Power
spectra of 108 days are compared showing systematic differences between
mode frequencies measured in intensity and in velocity. Data coverage
exceeds 97% for all the instruments during this interval. The weighted
mean differences (V-I) are −0.1 µHz for l=0, and −0.16 µHz for
l=1. The source of this systematic difference may be due to an asymmetry
effect that is stronger for modes seen in intensity. Wavelet analysis
is also used to compare the shape of the forcing functions. In these
data sets nearly all of the variations in mode amplitude are of solar
origin. Some implications for structure inversions are discussed.
---------------------------------------------------------
Title: On the direction of the rotation axis of the Sun
Authors: Gizon, L.; Appourchaux, T.
1997BAAS...29R1121G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Contribution of Low-l p Modes to the Solar Equatorial Rotation
Profile
Authors: Rabello Soares, M. C.; Roca Cortés, T.; Jiménez, A.;
Appourchaux, T.; Eff-Darwich, A.
1997ApJ...480..840R Altcode:
The solar equatorial velocity profile is known down to the base of the
convection zone with high precision (<=1%) from here downward until
approximately 0.5 R<SUB>⊙</SUB>, it seems to be constant, independent
of latitude, and lower than the equatorial surface rate. This result
comes from the inversion of high-l p-mode observations (Thompson
et al. 1996), while low-l p modes, which penetrate deeper, are not
measured to the precision required. Recently, new results from the
LOWL instrument on such modes suggest that deeper down, the rotation
rate could be even slower (Tomczyk, Schou, & Thompson 1995a). Here
results from LOI-T, a low-resolution high-precision photometer, are
presented and analyzed to yield accurate measurements of the frequencies
and splittings of modes with 2 <= l <= 8. The accuracy of the
frequency determinations and the agreement with the best results
yielded by low- and high-l instruments give credit to the results and
show its capability as an intercalibrating tool for experiment. The
splittings found, combined with those of GONG (high-l modes), are
used to perform an inversion of the equatorial rotation profile in the
radiative interior; the result found is that the region from 0.2 <=
r/R<SUB>⊙</SUB> <= 0.4 rotates slower than the surface rate.
---------------------------------------------------------
Title: Study of the Effect of Active Regions on the Solar Irradiance
During Solar Minimum
Authors: Domingo, V.; Sanchez, L.; Appourchaux, T.; Froehlich, C.;
Wehrli, C.; Hoeksema, T.; Pap, J.
1997SPD....28.0206D Altcode: 1997BAAS...29..893D
We have determined both the size of the area that contributes to the
solar irradiance increase around an active region and the angular
distribution of the radiance excess in it, using data obtained during
about one year around solar minimum (April 1996 - April 1997). During
the solar minimum and the early raising phase of the new maximum it
is possible to study the effect of isolated active regions while there
are few of them. The result of this study will be important to separate
the contribution of the active regions to the solar irradiance change
during the solar cycle from any underlying long term effect, if there
is one. The solar radiance measured by the Low-resolution Oscillations
Imager (LOI) of the VIRGO instrument and by the MDI instrument aboard
SOHO is used to determine the dimension of the radiating area. The
increase in irradance is determined by the Sun Photometers (SPM)
and Radiometers on the VIRGO instrument.
---------------------------------------------------------
Title: The Effects of Systematic Errors in the Estimation of p-Mode
Frequencies on the Inversion of Solar Internal Structure
Authors: Rhodes, E. J., Jr.; Appourchaux, T.; Bachmann, K.; Kosovichev,
A. G.; Scherrer, P. H.; Schou, J.; Reiter, J.
1997SPD....28.0901R Altcode: 1997BAAS...29..913R
The frequencies and associated uncertainties of the low-, intermdeiate-,
and high-degree p-mode oscillations are the input quantities for the
inversion programs which infer the thermodynamic structure of the solar
interior. In this review we will attempt to demonstrate the different
possible systematic errors that are currently present in our estimation
of both the modal frequencies and their uncertainties. We will also
demonstrate the effects of some of these errors upon the inferred
radial profile of the solar internal sound speed. Among the different
possible systematic errors which we will discuss are the effects of:
1)the asymmetric shapes of the peaks in observational power spectra,
2)the realization noise which is present in the case of the low-degree
modes, 3)the different frequency estimation methods used on different
types of power spectra (i.e., on either tesseral power spectra or
on m-averaged power spectra), 4) the differences in the frequencies
which are estimated from velocity- and intensity-based power spectra,
5) the blending of individual p-modes into so-called "ridges" of
observed power at both high degrees and high frequencies, and 6) the
spatial and temporal aliasing which occurs at both high degrees and
at high frequencies. We will demonstrate these different errors using
results obtained with the VIRGO and MDI experiments onboard the SOHO
spacecraft. We will also compare some of these space-based results
with the results of similar estimates obtained from co-temporaneous
ground-based observations, such as from the Mt. Wilson 60-Foot Solar
Tower. We will include the results from different structural inversions
carried out with different sets of input frequencies and uncertainties
in order to demonstrate the effects of these different systematic
errors upon the inverted internal sound speed profile.
---------------------------------------------------------
Title: An estimate of the solar background irradiance power spectrum.
Authors: Rabello-Soares, M. C.; Roca Cortes, T.; Jimenez, A.; Andersen,
B. N.; Appourchaux, T.
1997A&A...318..970R Altcode:
Knowledge of the solar irradiance background is of great importance
to solar and stellar physics. In particular, its contribution
to the solar oscillations power spectrum is highly relevant as it
represents the ultimate limit to the sensitivity of solar oscillations'
observations. An analysis of the power spectra of the solar photometric
data coming from four different instruments - two space-borne (ACRIM
and IPHIR) and two earth-based instruments (SLOT and LOI-T) - has
been performed to obtain the upper limit to the solar irradiance
background's spectrum. These observations have been compared to a
numerical model computed for the non-coherent solar surface phenomena,
namely granulation, mesogranulation and supergranulation. There is an
overall good agreement between the general trend of the model and the
observed data.
---------------------------------------------------------
Title: First results from VIRGO on SoHO
Authors: Frohlich, C.; Andersen, B. N.; Appourchaux, T.; Berthomieu,
G.; Crommelynck, D. A.; Domingo, V.; Fichot, A.; Finsterle, W.;
Gómez, M. F.; Gough, D.; Jiménez, A.; Leifsen, T.; Lombaerts, M.;
Pap, J. M.; Provost, J.; Roca Cortés, T.; Romero, J.; Roth, H. -J.;
Sekii, T.; Telljohann, U.; Toutain, T.; Wehrli, C.
1997IAUS..181...67F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: In-Flight Performance of the Virgo Luminosity Oscillations
Imager Aboard SOHO
Authors: Appourchaux, Thierry; Andersen, Bo N.; Fröhlich, Claus;
Jiménez, Antonio; Telljohann, Udo; Wehrli, Christoph
1997SoPh..170...27A Altcode:
The Luminosity Oscillations Imager (LOI) is a part of the VIRGO
instrument aboard the Solar and Heliospheric Observatory (SOHO). The
scientific objective of the LOI experiment is to identify and
characterize pressure and internal gravity oscillations of the Sun by
observing the radiance variations. The LOI is a low-resolution imager
with 12 pixels, for the measurement of the radiance distribution
over the solar disk at 500 nm. The low resolution capability of the
instrument allows the identification of individual azimuthal orders
for l = 0 to 7, without suffering the mixing that affects integrated
solar disk instruments. The performance, calibrations and instrumental
effects of the LOI are described together with the procedures for
extracting the solar p modes.
---------------------------------------------------------
Title: First Results from VIRGO, the Experiment for Helioseismology
and Solar Irradiance Monitoring on SOHO
Authors: Fröhlich, Claus; Andersen, Bo N.; Appourchaux, Thierry;
Berthomieu, Gabrielle; Crommelynck, Dominique A.; Domingo, Vicente;
Fichot, Alain; Finsterle, Wolfgang; Gómez, Maria F.; Gough, Douglas;
Jiménez, Antonio; Leifsen, Torben; Lombaerts, Marc; Pap, Judit M.;
Provost, Janine; Roca Cortés, Teodoro; Romero, José; Roth, Hansjörg;
Sekii, Takashi; Telljohann, Udo; Toutain, Thierry; Wehrli, Christoph
1997SoPh..170....1F Altcode:
First results from the VIRGO experiment (Variability of solar IRradiance
and Gravity Oscillations) on the ESA/NASA Mission SOHO (Solar and
Heliospheric Observatory) are reported. The observations started
mid-January 1996 for the radiometers and sunphotometers and near the
end of March for the luminosity oscillation imager. The performance of
all the instruments is very good, and the time series of the first 4-6
months are evaluated in terms of solar irradiance variability, solar
background noise characteristics and p-mode oscillations. The solar
irradiance is modulated by the passage of active regions across the
disk, but not all of the modulation is straightforwardly explained in
terms of sunspot flux blocking and facular enhancement. Helioseismic
inversions of the observed p-mode frequencies are more-or-less in
agreement with the latest standard solar models. The comparison of
VIRGO results with earlier ones shows evidence that magnetic activity
plays a significant role in the dynamics of the oscillations beyond
its modulation of the resonant frequencies. Moreover, by comparing
the amplitudes of different components ofp -mode multiplets, each of
which are influenced differently by spatial inhomogeneity, we have
found that activity enhances excitation.
---------------------------------------------------------
Title: VIRGO: Experiment for Helioseismology and Solar Irradiance
Monitoring
Authors: Fröhlich, Claus; Romero, José; Roth, Hansjörg; Wehrli,
Christoph; Andersen, Bo N.; Appourchaux, Thierry; Domingo, Vicente;
Telljohann, Udo; Berthomieu, Gabrielle; Delache, Philippe; Provost,
Janine; Toutain, Thierry; Crommelynck, Dominique A.; Chevalier,
André; Fichot, Alain; Däppen, Werner; Gough, Douglas; Hoeksema,
Todd; Jiménez, Antonio; Gómez, Maria F.; Herreros, José M.; Cortés,
Teodoro Roca; Jones, Andrew R.; Pap, Judit M.; Willson, Richard C.
1995SoPh..162..101F Altcode:
The scientific objective of the VIRGO experiment (Variability of solar
IRradiance and Gravity Oscillations) is to determine the characteristics
of pressure and internal gravity oscillations by observing irradiance
and radiance variations, to measure the solar total and spectral
irradiance and to quantify their variability over periods of days to
the duration of the mission. With these data helioseismological methods
can be used to probe the solar interior. Certain characteristics of
convection and its interaction with magnetic fields, related to, for
example, activity, will be studied from the results of the irradiance
monitoring and from the comparison of amplitudes and phases of the
oscillations as manifest in brightness from VIRGO, in velocity from
GOLF, and in both velocity and continuum intensity from SOI/MDI. The
VIRGO experiment contains two different active-cavity radiometers for
monitoring the solar `constant', two three-channel sunphotometers (SPM)
for the measurement of the spectral irradiance at 402, 500 and 862 nm,
and a low-resolution imager (LOI) with 12 pixels, for the measurement
of the radiance distribution over the solar disk at 500 um. In this
paper the scientific objectives of VIRGO are presented, the instruments
and the data acquisition and control system are described in detail,
and their measured performance is given.
---------------------------------------------------------
Title: An Attempt to Estimate the Intensity Background Spectra
Authors: Rabello Soares, M. C.; Roca Cortés, T.; Jiménez, A.;
Appourchaux, T.
1995ESASP.376b.397R Altcode: 1995help.confP.397R; 1995soho....2..397R
No abstract at ADS
---------------------------------------------------------
Title: The Luminosity Oscillations Imager on Board Virgo: Design
and Performances
Authors: Appourchaux, T.; Telljohann, U.; Martin, D.; Fleur, J.;
Lévêque, S.
1995ESASP.376b.359A Altcode: 1995soho....2..359A; 1995help.confP.359A
No abstract at ADS
---------------------------------------------------------
Title: Results from the Luminosity Oscillations Imager
Authors: Appourchaux, T.; Toutain, T.; Jiménez, A.; Rabello Soares,
M. C.; Andersen, B. N.; Jones, A. R.
1995ESASP.376b.265A Altcode: 1995help.confP.265A; 1995soho....2..265A
No abstract at ADS
---------------------------------------------------------
Title: Preliminary Analysis of the Radius Signal on Loi-T
Authors: Rabello-Soares, M. C.; Appourchaux, T.; Jiménez, A.; Roca
Cortés, T.
1995ESASP.376b.365R Altcode: 1995help.confP.365R; 1995soho....2..365R
No abstract at ADS
---------------------------------------------------------
Title: Solar P-Mode Frequencies from the IRIS Network
Authors: Gelly, B.; Fossat, E.; Palle, P.; Appourchaux, T.;
Eghamberdiev, S.; Fierry-Fraillon, D.; Grec, G.; Hoeksema, J. T.;
Khalikov, S.; Lazrek, M.; Loudagh, S.; Pantel, A.; Regulo, C.; Sanchez,
L.; Schmider, F. X.
1995ESASP.376b.373G Altcode: 1995help.confP.373G; 1995soho....2..373G
No abstract at ADS
---------------------------------------------------------
Title: Frequencies and splittings of low-degree solar P modes:
results of the Luminosity Oscillations Imager.
Authors: Appourchaux, T.; Toutain, T.; Telljohann, U.; Jimenez, A.;
Rabello-Soares, M. C.; Andersen, B. N.; Jones, A. R.
1995A&A...294L..13A Altcode:
The Luminosity Oscillations Imager is a part of the VIRGO instrument
to be flown aboard the Solar and Heliospheric Observatory in mid
1995. Using a ground-based version of the instrument, we have detected
low-l modes with a time series spanning 163 days. The low resolution
capability of the instrument allows the identification of individual
tesseral orders for l=2 to 5. The data reduction method prevents from
observing the l=0 modes, and reduces the amplitude of the l=1 modes with
m=+/-1. The frequencies and, for the first time, the linear component
of the mode splitting (a_1_) are given for l=2 to 5 for each order
n. The frequencies and the a_1_ are obtained by fitting simultaneously
the 2l+1 spectra using maximum likelihood estimators. The splittings
are compared with other published values.
---------------------------------------------------------
Title: STARS: A Proposal for a Dedicated Space Mission to Study
Stellar Structure and Evolution
Authors: Fridlund, M.; Gough, D. O.; Jones, A.; Appourchaux, T.;
Badiali, M.; Catala, C.; Frandsen, S.; Grec, G.; Roca Cortes, T.;
Schrijver, K.
1995ASPC...76..416F Altcode: 1995gong.conf..416F
No abstract at ADS
---------------------------------------------------------
Title: Testing the Statistical Significance of the Asymmetries of
p-Mode Line Profiles: Application to the IPHIR Data
Authors: Appourchaux, T.; Toutain, T.; Gough, D. O.; Kosovichev, A.
1995ASPC...76..314A Altcode: 1995gong.conf..314A
No abstract at ADS
---------------------------------------------------------
Title: VIRGO - the Solar Monitor Experiment on SOHO
Authors: Appourchaux, T.; Domingo, V.; Frohlich, C.; Romero, J.;
Wehrli, C.; Andersen, B. N.; Berthomieu, G.; Delache, P.; Crommelynck,
D.; Jimenez, A.; Roca Cortes, T.; Jones, A. R.
1995ASPC...76..408A Altcode: 1995gong.conf..408A
No abstract at ADS
---------------------------------------------------------
Title: Frequencies and splittings of low-degree solar p modes:
Results of the Luminosity Oscillations Imager
Authors: Appourchaux, T.
1995HiA....10..336A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Maximum likelihood estimators: an application to the estimation
of the precision of helioseismic measurements.
Authors: Toutain, T.; Appourchaux, T.
1994A&A...289..649T Altcode:
In this paper we apply the theory of Maximum Likelihood estimators to
determine the precision of parameters in fitting Lorentzian profiles
to helioseismic power spectra. The precision of frequency, linewidth,
amplitude and noise determination for a single p mode, and of the l=1
splitting, are derived as a function of the signal-to-noise ratio
and the spectral resolution of the spectrum. Libbrecht's formula
(Libbrecht 1992) for frequency precision is derived in a more general
case. For validating the approach, the theoretical precisions are
compared with those obtained with Monte-Carlo simulations and with
IPHIR observations. The robustness of the precisions obtained is ideal
for predictive purposes. The method used to derive the precisions is
general enough so that it can be used for others purposes.
---------------------------------------------------------
Title: STARS - an investigation of stellar structure and evolution.
Authors: Fridlund, M.; Appourchaux, T.; Pace, O.; Volunte, S.
1994ESAJ...18..247F Altcode:
STARS is a mission targeted at the understanding of stellar physics,
by carrying the established technique of helioseismology into the
new field of asteroseismology. This requires the measurement of
the miniscule variations in the light output of a stellar object
that result when acoustical waves hit the outer boundary of its
surface. These waves penetrate to the very center of the object and
thus carry information about the interior. In order to detect these
variations, STARS will have to carry the measuring of stellar flux to
new limits. Intimately coupled to the properties of the stellar interior
is the surface activity. A second part of the STARS experiment focuses
on time-resolved observations of this activity, providing information
about the outer boundary of the star, stellar rotation and angular
momentum transport, as well as magnetic and chromospheric acitivity.
---------------------------------------------------------
Title: PRISMA - Probing Rotation and Interior of Stars:
Microvariability and Activity. Report on the phase A study.
Authors: Appourchaux, T.
1993pris.book.....A Altcode:
The PRISMA mission addresses one of the most fundamental areas of
astronomy: the structure and evolution of the stars. It uses the new
technique of asteroseismology, measuring the surface amplitude of
oscillations which penetrate deep into the interior of stars, whilst
simultaneously monitoring surface activity.
---------------------------------------------------------
Title: Prisma - the First Space Mission to See Inside the Stars
Authors: Appourchaux, T.; Gough, D. O.; Catala, C.; Frandsen, S.;
Frohlich, C.; Hoyng, P.; Jones, A.; Lemaire, P.; Tondello, G.; Weiss,
W. W.
1993ASPC...42..411A Altcode: 1993gong.conf..411A
No abstract at ADS
---------------------------------------------------------
Title: Stellar seismology and activity: the need to go to space
(PRISMA) (invited paper)
Authors: Appourchaux, T.; Catala, C.; Catalano, S.; Frandsen, S.;
Jones, A.; Lemaire, P.; Weiss, W. W.
1993MmSAI..64..415A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: PRISMA. Probing Rotation and Interior of Stars:
Microvariability and activity
Authors: Appourchaux, T.; Catala, C.; Cornelisse, J.
1993ppri.book.....A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: PRISMA - the first space mission to see inside the stars.
Authors: Appourchaux, T.; Fridlund, M.; Cornelisse, J.; Volonté, S.
1993ESAJ...17..239A Altcode:
The PRISMA - Probing Rotation and Interior of Stars: Microvariability
and Activity - mission addresses one of the most fundamental areas
of astronomy: the structure and evolution of stars. It uses the new
technique of asteroseismology, measuring the surface manifestation of
oscillations that penetrate deep into the interiors of stars, whilst
simultaneously monitoring surface activity.
---------------------------------------------------------
Title: PRISMA: Probing Stars from Core to Corona
Authors: Appourchaux, T.; Catala, C.; Catalano, S.; Fransden, S.;
Fröhlich, C.; Gough, D. O.; Hoyng, P.; Jones, A.; Lemaire, P.;
Tondello, G.; Weiss, W.
1993ASSL..183..505A Altcode: 1993pssc.symp..505A
No abstract at ADS
---------------------------------------------------------
Title: PRISMA: a new space mission for stellar physics.
Authors: Appourchaux, T.; Gough, D.; Hyoyng, P.; Catala, C.; Frandsen,
S.; Froehlich, C.; Jones, A.; Lemaire, P.; Tondello, G.; Weiss, W. W.
1993ASPC...40..812A Altcode: 1993ist..proc..812A; 1993IAUCo.137..812A
This paper mainly focuses on the scientific objectives that can be
achieved with a new space mission of the European Space Agency -
PRISMA (Probing Rotation and Interior of Stars: Microvariability
and Activity). The scientific objectives can be classified into
three areas of interest: (1) Stellar structure and evolution. (2)
Stellar atmospheres and magnetic fields. (3) Stellar dynamics and
stellar dynamos.
---------------------------------------------------------
Title: Passive thermal control of a multilayer filter for space-based
solar observations.
Authors: Appourchaux, Thierry; Cislaghi, Massimo
1992OptEn..31.1715A Altcode:
Temperature distributions inside multilayer filters are often
required to assess performance. This subject is rarely treated in the
literature. Guidelines were developed that can be used to calculate a
thermal model for various applications. In this study the guidelines
are applied to an optical filter. This filter, which is not actively
thermally controlled, is the front element in a space experiment
devoted to the observation of solar intensity fluctuations. Temperature
distributions were calculated for different designs. The final design
minimizes temperature gradients, as well as degradation effects due to
UV and particle radiation. The effect of space exposure on temperature
distributions inside the filter is also addressed.
---------------------------------------------------------
Title: ESA's report to the 29th COSPAR Meeting
Authors: Appourchaux, T.; Chicarro, A.; Domingo, V.; Fridlund, M.;
Huber, M.; Innocenti, L.; Jakobsen, P.; Kessler, M.; Lebreton, J. P.;
Parmar, A.
1992wadc.meet.....A Altcode:
All ESA missions in operation, under development, or in planning are
described. Missions beyond the operational phase are also presented
if considerable effort is still being expended in supporting the data
analysis through an archive. The aging and completed missions are:
IUE, Exosat, Hipparcos, Giotto extended mission, Ulysses, and Hubble
Space Telescope. The projects under development are: Infrared Space
Observatory (ISO), the Solar Terrestrial Science Program (STSP) (which
comprises the four Cluster spacecraft and the Solar and Heliospheric
Observatory (SOHO)), the X-ray Multimirror Mission (XMM) and the
Cassini/Huygens mission. Missions under study are: the Far Infrared
Space Telescope (FIRST), the comet nucleus sample return (Rosetta),
the International Gamma Ray Laboratory (INTEGRAL), a network of three
semi hard landers to be placed on the Martian surface (MARSNET), a
mission for probing the interior and rotation of stars (PRISMA), and
a Satellite Test of the Equivalence Principle (STEP). Missions beyond
Horizon 2000 are: Return to the Moon, interferometry from space, and
Vulcan. ESA platforms described are Eureca (the European retrieval
carrier) and Simuris (a solar system and stellar interferometric
mission for ultrahigh resolution imaging and spectroscopy).
---------------------------------------------------------
Title: PRISMA: A Space Facility for Studying the Rotation; Interior
of Stars
Authors: Lemaire, P.; Appourchaux, T.; Jones, A.; Catala, C.; Catalano,
S.; Frandsen, S.; Weiss, W.
1992ASPC...26..643L Altcode: 1992csss....7..643L
No abstract at ADS
---------------------------------------------------------
Title: Prisma - a Space Facility for Studying Rotation and Activity
Authors: Lemaire, P.; Appourchaux, T.; Catala, C.; Catalano, S.;
Frandsen, S.; Jones, A.; Weiss, W.
1991ASIC..340..397L Altcode: 1991amey.conf..397L
No abstract at ADS
---------------------------------------------------------
Title: PRISMA: Probing Rotation and Interior of
Stars. Microvariability and activity
Authors: Appourchaux, T.; Catala, C.; Catalano, S.
1991ppri.book.....A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Prisma-probing rotation and interior of stars: Microvariability
and activity
Authors: Lemaire, P.; Appourchaux, T.; Catala, C.; Catalano, S.;
Frandsen, S.; Jones, A.; Weiss, W.
1991AdSpR..11d.141L Altcode: 1991AdSpR..11..141L
The measurement of frequencies, amplitudes and lifetimes of solar
oscillations has proven to be a very powerful tool to sound the
properties of the solar internal structure. Combined with observations
of emerging solar magnetic field parameters of the solar internal
structure and dynamo can be inferred. The same techniques may be
used to sound stellar interiors: asteroseismology and observation
of magnetic activity (emerging magnetic fields). The observation of
photometric fluctuations down to micromagnitudes on stars along or
near the main sequence when complemented with measurements of activity
levels will provide a wealth of information on the internal structure
and rotation rates, and its evolutions with age. The PRISMA mission
is an ESA Assessment Study currently underway. We present here the
scientific objectives of the mission, the measurements to be made, the
techniques to be used, and the main characteristics of a model payload.
---------------------------------------------------------
Title: Observations of Low-Degree Solar Oscillations with Few
Detector Elements
Authors: Appourchaux, T.; Andersen, B. N.
1990SoPh..128...91A Altcode: 1990IAUCo.121P..91A
The detection of low-degree solar oscillation modes with a specific
low-resolution detector configuration is investigated. The detector is
part of an instrument (the Luminosity Oscillations Imager) in the VIRGO
package, to be flown on SOHO. Various problems such as p- and g-mode
sensitivity, B and roll angle effects, modes isolation, cross-talk and
guiding effects are treated for a given detector configuration. The
computed sensitivity will enable the instrument to detect any type of
modes for l < 6.B and roll angle effects can be compensated by using
adequate filters for mode isolation. Guiding effects are small for
p-modes. Also some other complex high-degree mode effects are treated.
---------------------------------------------------------
Title: ESA's report to the 28th COSPAR meeting, The Hague
(Netherlands), Jun 1990.
Authors: Appourchaux, T.; Burke, W. R.
1990ert..book.....A Altcode:
This report, presented to COSPAR's biennial meeting, covers
the period May 1989 to April 1990. It describes all missions in
the planning stage and under development, as well as missions in
operation. Missions beyond the operational phase are also presented,
if considerable effort is still being expended on establishing data
bases or on data analysis. Contents: 1. Introduction. 2. On-going
& completed missions: IUE, Exosat, Hipparcos, Giotto extended
mission. 3. Projects under development: Ulysses, Hubble Space Telescope,
ISO, STSP (The Solar-Terrestrial Science Programme), Cassini/Huygens,
XMM. 4. Missions under study: Cornerstone missions (FIRST, Rosetta),
assessment studies, Third Millenium missions (Mars exploration,
interferometry from space, Vulcan). 5. Platforms: Eureca A, Columbus
Polar Platform. 6. Bibliography.
---------------------------------------------------------
Title: Optimization of parameters for helioseismology experiments
measuring solar radial velocities
Authors: Appourchaux, T.
1989A&A...222..361A Altcode:
Solar-oscillation instruments have many common characteristics,
such as detecting solar radial velocities on Fraunhofer lines with a
2-point measuring technique, high spectral resolution and stability,
etc. The 2-point measuring technique is described including spectral
responses of filter and blocker, calibration, sensitivity and photon
noise. Optimization of different parameters such as filter profile,
filter bandwidth, filter scanning range, line profile, line depth and
prefilter bandwidth is addressed by means of a simple model. This
analysis is then applied to existing or future helioseismology
instruments.
---------------------------------------------------------
Title: The stable solar analyzer.
Authors: Rust, D. M.; Appourchaux, T.
1988ESASP.286..227R Altcode: 1988ssls.rept..227R
This paper presents a progress report on the development of an
instrument with very high (1:10<SUP>10</SUP>) wavelength stability
designed to measure solar surface velocities and magnetic fields. The
instrument determines Doppler and Zeeman shifts in solar spectral lines
by a 6-point weighted average. It is built around an electrically
tunable solid lithium-niobate Fabry-Perot etalon that is stabilized
against a diode laser which itself is locked to a resonance line
of cesium 133. Key features are the unique etalon, which acts as a
wide-angle 0.017-nm solar filter, the camera with a specially stabilized
shutter, and the instrument control and data collection system. Use
of the instrument in helioseismological research is emphasized.
---------------------------------------------------------
Title: Solar oscillations instrumentation and measurement theory.
Authors: Appourchaux, T.
1988ESASP.286..595A Altcode: 1988ssls.rept..595A
Solar-oscillation instruments have many common characteristics, such as
detecting solar radial velocities on Fraunhofer lines with a 2-point
measuring technique, high spectral resolution and stability, etc... A
review of these common effects is made which can be used for optimizing
most instruments in helioseismology. The choice of the spectral line
is addressed for getting a high signal to solar noise ratio. Velocity
imaging of solar oscillations modes is detailed including spatial
sampling and span, highest observable degree. Applications of these
different analysis is then applied to existing or future helioseismology
instruments.
---------------------------------------------------------
Title: Performance of a Stabilized Fabry-Perot Solar Analyzer
Authors: Rust, D. M.; Appourchaux, T.; Hill, F.
1988IAUS..123..475R Altcode:
A unique solar lineshift analyzer described by Rust, Burton and Leistner
(1986) has been used to study solar oscillations. Operation of this
"Stabilized Solar Analyzer" depends on the electro-optic effect in
crystalline lithium niobate, the substrate of the solid Fabry-Perot
etalon. For 10 days in February, 1986, at the Vacuum Tower Telescope
of the Sacramento Peak Observatory, the authors obtained full-disk
observations of the solar oscillations.
---------------------------------------------------------
Title: Rotation in the Solar Convection Zone Inferred from Fabry-Perot
Observations of the 5-MIN Oscillations
Authors: Hill, F.; Rust, D. M.; Appourchaux, T.
1988IAUS..123...49H Altcode:
Full disk observations of the 5-min solar oscillations have been
obtained with a lithium niobate Fabry-Perot filter. The equatorial
solar rotation rate as a function of depth has been inferred from the
sectoral modes of oscillation using the Backus-Gilbert optimal averaging
inversion method. The results show a rotation rate that slowly decreases
over the depths of 15 to 56 Mm below the photosphere. The results are
in agreement with the previous Duvall-Harvey observations.
---------------------------------------------------------
Title: The Faraday effect in a magneto-optical filter.
Authors: Appourchaux, T.
1987SoPh..109..393A Altcode:
A magneto-optical filter was built to establish its utility for
measuring solar oscillations. A theoretical model is described and
the asymptotic behaviour of the Faraday effect in the filter is
deduced. Experimental work confirms to first order the asymptotic model.
---------------------------------------------------------
Title: Observations of Solar Oscillations with a Fabry-Perot Etalon
Authors: Rust, D. M.; Hill, F.; Appourchaux, T.
1987BAAS...19R.933R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Correction of Atmospheric Transparency Gradient Effect on
Solar Radial Velocities
Authors: Appourchaux, T.
1984srps.conf..117A Altcode:
The author has found that the major part of the atmospheric gradient
is that computable from sec z and standard atmospheric tables. Thus
a reasonable first approximation of the velocity correction can be
obtained simply by computation. The autor has demonstrated a simple
system for measuring the actual gradient from which the effective
spurious velocity can be computed using standard figures for limb
darkening and solar rotation.
---------------------------------------------------------
Title: Développement d'un Fabry-Perot destiné à l'observation des
oscillations solaires pour une mission spatiale
---------------------------------------------------------
Title: Développement
d'un Fabry-Perot destiné à l'observation des oscillations solaires
pour une mission spatiale
---------------------------------------------------------
Title: Development of a Fabry-Perot
interferometer for the observation of solar oscillations from a
space mission;
Authors: Appourchaux, Thierry
1984PhDT........97A Altcode:
No abstract at ADS