file: rob-notes.txt = Rob Rutten notes on HAO course April 2003 last: May 1 2003 init: Apr 16 2003 note: @ = todo item Rob's stuff =========== RTSA = RJR web lecture notes SSA = Stellar Spectra A exercises (RJR website) SSB = Stellar Spectra B exercises (RJR website) SSC = Stellar Spectra C exercises (to be produced?) GTR = light-blue lecture notes in my office (only one paper copy here) GTR Chapts 2-5 = extended version of Rybicky & Lightman Chapt 1 GTR Chapt 6 = summary of Rybicky & Lightman Chapts 2-7 RTA Chapt 2 = summary GTR Chapts 2-5 RTA Chapt 3-4 = roughly similar to Mihalas 1st edition (easier) people ====== Eirik Endeve eendeve@ucar.edu Holly Gilbert iggy@ucar.edu Anna Pietarila annap@ucar.edu Tom Holzer holzer@ucar.edu Egil Leer leer@ucar.edu Alexei Semenov asemenov@ucar.edu Rob Rutten R.J.Rutten@astro.uu.nl (rrutten@ucar.edu but only temporarily) course plan = mainly Chapts 2+5 RTSA ==================================== photon-atom interactions (Chapt 2 RTSA) bb, bf, ff, Thomson, Rayleigh pairs: 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_radial S = (1-eps) J + eps B basic radiative transfer (Chapt 2 RTSA) differential transport equation line formation for homogeneous thin/thick medium integral solution, Eddington-Barbier approximation schematic line formation plane-parallel atmosphere plane-parallel radiative transfer (Chapt 4 RTSA) Lambda and Phi operators and properties diffusion approximation demonstration scattering Eddington approximation ? numerical radiative transfer (Chapt 5 RTSA) Feautrier method lambda iteration ALI ? stellar atmospheres (Chapt 5 RTSA) empirical model determination classical stellar photospheres in LTE, HE, RE chromospheric line formation ? coronal radiation coronal equilibria coronal energy budget light and dark in TRACE 171 ============================================================================ daily logs ============================================================================ Apr 16 2003 =========== start, choice course size and content 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 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 Eirik's nose shows Na D lines in daylight non-local anything illuminated by sunlight shows Na D lines except corona white-light corona (solar eclipse) Thomson (electron) scattering of photospheric light lots of electrons due to large degree of ionization large Dopplershifts from high temperature wash out spectral lines blue sky = Rayleigh scattering off molecules (cross-section ~lambda^4) stellar-atmosphere particles: atoms, ions, electrons, molecules stellar-atmosphere RT processes: bb,bf,ff; Thomson, Rayleigh scattering Apr 17 2003 =========== repeat overview photon-matter interactions H-minus bf and ff extinction radiation quantities (Chapt 2 RTSA) definitions I, J, F; j, alpha; tau; S radiative transfer (Chapt 2 RTSA) differential transport equation integral solution homogeneous medium radial optical depth Apr 18 2003 =========== repeat basic process pairs: S=B (LTE) or S=J (scattering) repeat basic equations up to plane-parallel transport equation Eddington-Barbier approximation schematic line formation in optically thick media profile = extinction-weighted mapping of source function (height) absorption lines, emission lines, reversals coronal EUV absorption = bound-free H I, He I, He II? scattering recombination = fresh electron = complete frequency redistribution over edge profile = re-emission outside TRACE passband @ coronal EUV emission and equilibria bb coherent scattering versus complete redistribution generally assume latter = use profile-averaged mean intensity J^bar Apr 21 2003 =========== Zanstra mechanism for Balmer emission lines from planetary nebulae (Chapt 8 GTR) HI Ly-cont ionization followed by recombination + cascade Balmer photons escape, Lyman photons stay put (scatter) sum nebular Balmer emission = measure invisible stellar Ly-cont flux planetary spectra visible light peak = refelcted sunlight infrared peak = thermal emission planet itself (or its atmosphere) LTE line and continuum formation from the solar atmosphere lines: absorption = outward declining T, emission = outward increasing T edges: idem solar continuum (exercise SSB-2, Avrett graph in Chapt 8 GTR T-min between photosphere and chromosphere is sampled twice at 160 mum (increasing H-minus ff with increasing wavelength) at 1600 AA (inceasing bf-edges metals with decreasing wavelength) Apr 23 2003 =========== Einstein coefficients and relations rewriting extinction + emissivity into Einstein coefficients formal line source function Ca II K reversal formation again Apr 24 2003 =========== definition departure coefficients (RTSA Chapt 2) example Na D line source function (RTSA last chapter) simple treatment of two-level-atom scattering (RTSA Chapt 2) moments of the transport equation (RTSA Chapt 4) Schwarzschild equation Kourganoff Lambda operator plots Apr 28 2003 =========== lambda and phi operators (RTSA Chapt 4) radiative- equilibrium gradient S = 1 + 1.5 tau diffusion approximation Eddington approximation analytic results for Eddington approximation and linear B(tau) square root epsilon law for isothermal atmosphere Avrett results for complete redistribution Apr 30 2003 =========== VALIIIC = Nobel prize class paper = perfect plane parallel NLTE-NRE star construction of the model S B J continuum formation diagrams LTE in infrared since ff processes (H-min and H) heavily NLTE scattering in ultraviolet (bound-free edges metals) net cooling rate diagrams hydrogen balance Balmer-alpha photon losses against Balmer cont hesting Lyman-alpha losses dominant cooler in high layers Ca II H&K, MgII h&k, Mg b lines etc collers in mid-chromosphere didn't do ========= coronal equilibria dielectronic recombination numerical methods (Chapt 5) empirical model determination (Chapt 7) grey atmosphere (Chapt 7) RE grey atmosphere (Chapt 7) LTE versus NLTE line cooling (Chapt 7) Auer-Mihalas hot hydrogen-only RE atmosphere (final whopper problem) partial redistribution ("not yet") Ca II H&K with Carlsson-Stein shocks ("not yet")