file: masters.00 = Rob Rutten's course CAUP Masters December 2000 last: Dec 15 2000 note: @ = todo item RTSA = handed-out lecture notes GTR = light-blue lecture notes in teaching room (go to library) daily logs (time-reverse order) =============================== Friday December 15 = brief overview ------------------ radiation processes: bb, bf, ff, Thomson, Rayleigh radiative transfer: thin/thick; LTE/NLTE hot stars = Thomson NLTE, cool stars = H-minus LTE strong lines always epsilon << 1 due to density drop coronal equilibrium bright and dark in TRACE images Na D lines: Steven Weinberg quote "human comfort" but solar Stokes Q linear polarization not understood @ note on research possibilities for Damien-Darren-Rajib: I may have opportunities in Utrecht, smaller probability than Carla's ESMN slot in Naples - but who knows. Suggestion is to get in contact in early February if you are interested. Thursday December 14 = solar corona; stellar atmosphere modeling --------------------- solar corona (GTR Chapt 8) white light K (= Kontinuum) corona white light = photospheric sun light but no Fraunhofer lines due Thomson scattering off free electrons with Doppler motions wash-out of lines = 100 km/s = temperature 10^6 K white light F (= Fraunhofer) corona photospheric lines present from scattering off dust particles visible "coronium" lines = fine-structure Fe X transition thermal emission = X-ray lines collisional excitation, spontaneous de-excitation = energy loss combined radiation loss equals unknown coronal heating (magnetic) classical stellar atmospheres (RTSA Chapt 7) basic parameters T_eff, log g, metallicity, microturbulence=fudge gas pressure from temperature through hydrostatic equilibrium "model" = temperature stratification from - solar limb darkening = original method that established H-minus - solar/stellar continuum (opacity varoation samples depths) - solar/stellar lines (idem) - assumption of radiative equilibrium grey model Rosseland mean extinction solar models: photosphere is very close to radiative equilibrium hot stars: continuous opacity dominated by Thomson scattering NLTE continuum, no avelength variation => Auer-Mihalas modeling put files in ~rutten/masters at CAUP cluster: drwxr-xr-x 2 rutten visitors 8192 Dec 13 22:27 rtsa/ drwxr-xr-x 2 rutten visitors 8192 Dec 13 23:21 ssa/ drwxr-xr-x 2 rutten visitors 8192 Dec 13 23:22 ssb/ rtsa = lecture notes in clickable pdf format (use acroread) ssa = exercises Stellar Spectra A ssb = exercises Stellar Spectra B @ Recommended exercises: ssa2, ssa3, ssb1, ssb2 = same stuff as course (ssa1 = spectral classification, too simple; ssb3 = compute solar NaD lines, too much) Wednesday December 13 = LTE and NLTE radiative transfer --------------------- spectral lines from stellar atmosphere = mapping S(h) through tau_nu four-panel formation diagrams = RTSA Fig. 2.5 solar brighness continuum = inverse mapping of coninuous extinction in particular H-minus bf and ff @ = IDL exercise SSB2 "Continuous spectrum from the solar atmosphere" LTE assumption (RTSA 2.5) matter: Maxxwell, Boltzmann, Saha radiation: Planck, Wien, Rayleigh-Jeans Payne identification of spectral classification as Saha-Boltzmann T @ = IDL exercise SSA2 "Saha-Boltzmann calibration of the Harvard sequence" NLTE line formation equation system (RTSA 2.6.1) numerical solution = multi-D Newton-Raphson (RTSA Fig. 5.3) Tuesday December 12 = basic radiative transfer ------------------- blue sky = Rayleigh scattering off molecules (cross-section ~lambda^4) stellar-atmosphere particles: atoms, ions, electrons, molecules stellar-atmosphere processes: bb,b,f,ff; Thomson, Rayleigh scattering cool stars: H-minus bf and ff (no bb); ionization limiT 1.6 mum real atoms: also roundabout photon conversion next to two-level processes radiation quantities (RTSA Sect 2.1; GTR Chapt. 2) radiation transport (RTSA Sect 2.2; GTR Chapt 3) @ IDL: SSA nr. 3 = Minnaert-like Schuster-Schwarzschild line formation @ RTSA problem #1 (bound-free edges; page 223) Monday December 11 = basic radiation physics (Chapter 1 GTR) ------------------ What is spectrum of the whiteboard 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 whiteboard 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 atom-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 @ profile = delta function (pm: line broadening) 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 ions, molecules, hadrons etc @ pm: H-minus bf and ff = neutral hydrogen atom + second electron provides dominant continuous extinction in photospheres cool stars 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 @ rad exc + further exc to other levels etc = photon conversion nonthermal, nonlocal, non-monochromatic solar line formation = mixture of scattering + thermal photon production S = (1 - eps) J + eps B if eps << 1: difficult non-local integro-differential equation eps = photon destruction probability, scales with density thermal sample temperature at escape depth escape depth lies further out in line (smaller transparency) easy: production photons = B_\lambda (T) with outward decreasing temperature: absorption lines scattering needs evaluation of J = intensity averaged over all directions so needs I = radiative transport complex @ exercise = Minnaert-like Schuster-Schwarzschild line formation course content (summary) = Chapts 2+5 RTSA, Chapt 8 GTR ======================================================== photon-atom interactions (Chapt 2 RTSA) 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 line formation for homogeneous thin/thick medium integral solution, Eddington-Barbier approximation line formation optically thick objects stellar atmospheres (Chapt 5 RTSA) empirical model determination classical stellar photospheres in LTE, HE, RE chromospheric line formation coronal ionization equilibrium coronal energy equilibrium stellar environments (Chapt 8 GTR) P Cygni profiles hot-star winds Zanstra mechanism planetary nebulae lecture notes ============= RTSA = "Radiative Transfer in Stellar Atmospheres" thick notes, edition December 1 2000 (also available on WWW) one copy to each student; one copy to CAUP library Chapter 2 = quantities, processes, basic RT = summary of GTR Chapter 5 = classical stellar atmospheres GTR = "Generation and Transport of Radiation" light-blue notes; one copy in library March 1995 = Kiselman combine of Peterson translation + Chapts 2,3 IART no electronic version yet available Chapt 2-5 = RTSA Chapt 2 but GTR is much more extended RTSA Chapt 2 = summary of the GTR lecture notes Chapter 8 "Applications" is pertinent (corona's, planetary nebulae etc) books (+/- = present/not present in CAUP library) ================================================== see more extensive descriptions in introduction to RTSA + Rybicki & Lightman (CAUP library QB461 R88) + 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