file: masters.02 = Rob Rutten's course CAUP Masters December 2002 last: Dec 19 2002 site: /data/disk0/rutten/masters students -------- Joana Ascenso <97a004@astro.ma.fc.up.pt> Sandra Jorge Sean Donegan Rui Barros Alexandre Aib'eo Eoin Clerkin course material --------------- GTR = Generation and Transport of Radiation (CAUP library) RTSA = Radiative Transfer in Stellar Atmospheres (you have printout; CAUP library /home/rutten/masters/rtsa http://www.astro.uu.nl/~rutten) SSA = Exercises Stellar Spectra A you have printout also in my CAUP dir and on my website SSB = Exercises Stellar Spectra B also in my CAUP dir and on my website textbooks: see below course content (summary) = Chapts 2 RTSA, Chapt 8 GTR ------------------------ photon-atom interactions (Chapt 2 RTSA [= summary Chapt 4, 5, 6 GTR]) bb, bf, ff, Thomson, Rayleigh photon creation, destruction, scattering, conversion TE: Planck function, Boltzmann, Saha distributions local thermal (LTE) versus nonthermal nonlocal (scattering, conversion) radiation quantities (Chapt 2 RTSA) definitions I, J, F; j, alpha, S; tau, tau_rad S = (1-eps) J + eps B radiative transfer (Chapt 2 RTSA) differential transport equation integral solution, Eddington-Barbier approximation line formation optically thick objects two-level scattering solar spectrum (Chapt 8 GTR) stellar environments (Chapt 8 GTR) solar coronal radiation hot star winds: P Cygni profiles planetary nebulae: Zanstra conversion books (+/- = present/not present in CAUP library in 2000) ----- more extensive book descriptions in introduction to RTSA + Rybicki & Lightman (CAUP library QB461 R88) GTR is a much extended version of Chapter 1 of this book (but Chapter 6 of GTR is a summary of all other chapters of this book) + Gray (CAUP library QB809 G67) + Boehm-Vitense series lower level than RTSA but quite good; recommended + Shu I, II (CAUP library QB461 S5;1 and S5;2) higher level than RTSA; very good but pretty deep - Novotny (out of print) - Mihalas (out of print) and one that I hadn't seen before: + Don Emerson (CAUP library QB 465 E44) Interpreting Astronomical Spectra John Wiley & Sons 1996 looks quite good daily logs of what I taught =========================== Monday Dec 16 2002 = basic radiation physics ------------------ What is spectrum of the blackboard with lights off? solar! non-local and radiation T >> local emission T lots of scattering on the way but that is all monofrequent so very non-local: photons carry signature of solar creation even though observed from blackboard particle-photon interactions (RTSA 2, 3; GTR 1, 5, 6) bound-bound processes = discrete energy up/down => spectral lines radiative excitation collisional excitation spontaneous radiative deexcitation collisional deexcitation stimulated radiative deexcitation bound-free processes = ionization/recombination => continua same five basic possibilities profile: zero below threshold energy, drop-off above free-free processes = atom/ion + free electron => continua same five basic possibilities profile: no threshold, decrease with energy "atom" may also be ion, molecule, hadron etc Thomson scattering: free electrons, wavelength independent Rayleigh scattering: bound electrons, lambda^4 (blue sky) basic process combinations (for bb but same for bf and ff) (GRT 1) coll exc + rad deexc = photon creation rad exc + coll deexc = photon destruction these two are thermal and local rad exc + rad deexc = photon scattering nonthermal, nonlocal Kirchhoff-Bunsen sodium-in-flame experiments (RTSA 1; GTR 1) flame: Na D emission lines = coll exc + rad deexc plus background illumination: absorption lines due to scattering = redirection away from line of sight line strength increases with amount of Na diagnostic of presence and quantity of Na at a distance Na D lines in solar spectrum "all understood" but polarization still enigmatic total eclipse white light without Na D lines due to Doppler smearing = fast motions coronal electrons in Thomson scattering X-ray lines = thermal emission TE laws (RTSA 2; GTR 4) matter = Maxwell, Boltzmann, Saha spectral classification (Annie Cannon) identification spectral type = temperature Saha-Boltzmann (Cecilia Payne) SSA-2 exercise = Payne-like Saha-Boltzmann curves for "Schadeenium" Tuesday Dec 17 2002 = radiation quantities and transfer ------------------ radiation quantities I = intensity ergs / cm^2 s Hz ster = constant along ray F = net flux = sum in forward direction, cosine weighting J = mean intensity = average over all angles, same units radiation change quantities (RTSA 2, GTR 3) emissivity, extinction coefficient optical path length, optical depth source function TE laws (RTSA 2; GTR 4) radiation = Planck + Wien & Rayleigh-Jeans regimes two-level line source function S = (1-eps) J + eps B radiative transfer equation (RTSA2, GTR 3) differential form integral from solution for emergent intensity from plane-parallel atmosphere Eddington-Barbier relation explanation of the solar optical continuous spectrum (GTR 8) T_b continuum = inverse of continuous opacity continuous opacity visible and near-IR = H-minus (Chandrasekhar): extinction hump 400-1600 nm = H-minus bf, beyond 1.6micron = H-minus ff Wednesday Dec 17 2002 = Einstein coefficients, line formation --------------------- review of equations sofar (RTSA Chapt 2) bb transitions (RTSA 2, GTR 5) Einstein coefficients Einstein relations coherent scattering versus complete redistribution emissivity and extinction in Einstein coefficients stimulated emission as negative extinction general line source function line formation with the Eddington-Barbier approximation four-panel graphs explanation of the solar spectrum (GTR 8) T_b continuum = inverse of continuous opacity continuous opacity visible and near-IR = H-minus 2nd electron from donor elements = lower ionization energy than H VALIII model with spectral feature formation height Thursday Dec 18 2002 = wrap-up ends -------------------- brief equation review = radiative transfer rap (last page RTSA) lambda operator = formal solutin J from S = basic operator in numerical iterative solution NaD lines have dark cores due to scattering sqrt(eps) law: isothermal medium has S(0) = sqrt(eps) B(T) VALIIIC model solar atmosphere T_b plot Avrett (GTR Chapt 8) photospheric temperature decline: absorption lines, limb darkening chromospheric temparture rise: emission lines, liumb brightening coronal X-ray emission (GTR Chapt 8) X-ray = thermal emission, far from LTE due to optical thinness excitation equilibrium: depends on T and N_e ionization equilibrium: not dependent on N_e, only on T just reverse of Boltzann and Saha dielectronic recombination important Carole Jordan iron ion population graph X-ray absorption = bound-free HI, HI, HeII scattering out of passband planetary nebulae (GTR Chapt 8) Zanstra mechanism for Balmer-line emission Balmer emission lines nebular shell = converted Ly-cont photons sum Balmer photons shell = sum irradiating Lyman cont photons star