Yakiv V.Pavlenko Main astronomical observatory 27 Sabolotnoho, Kyiv, Ukraine www.mao.kiev.ua/staff/yp Model atmospheres and specra of hydef giants and peculiar stars
Collaborators J.Tennyson (UCL) Greg Harries (UCL) Yakovina Larisa(MAO) Kaminsky Bogdan (MAO) Hugh Jones (UH) Bob Barver (UCL) Nye Evans(Keele) Hilmar Duerbeck(OU) Sveta Zhukovska (MAO) Thomas Geballe (Gemini)
Stars of interest: Hydrogen-rich stars --- M-giants --- C-giants --- V838 Mon --- RS Oph Hydrogen poor stars ---R CrB et al. ---Sakurai’s object
Outline Model atmospheres and fits to SEDs Isotopic ratios (12C/13C) Abundances
PROCEDURE Model atmospheres SAM12 (ATLAS12) 1D, Convection + radiation, LTE, No sinks and sources of energy Opacity sampling for line opacity Synthetic spectra WITA 1D, LTE, Voigt function for lines VCS theory for H lines SEDs
OPACITIES: C/O < 1, Opacity sources: VO, TiO; H2O, CO Methane C/O > 1 CN, CO, CH, C2,HCN, C3, --- [H]?? --- isotopes!
Problems: • Opacities (missed continuum absorption in the blue, line lists (both atomic and molecular), isotops, • chemical abundances and equilibrium, • 3-D convection, • sphericity effects, • the dust, • stellar winds.
“...Given the web of interconnected uncertainties and errors presented here, one is initially tempted to give up on stellar atmospheres completely and turn to something simple like cosmology.” V.Trimble & R.A. Bell:
Astronomy often progresses amoeba- like: the advance in one pseudopod may not move the animal very far, but permits other parts to advance in their turn and can reveal portions of the organism that are in danger of being left behind. V.Trimble, R.A.Bell, Q.Jl.R.astr.Soc.(1981),22, 361-379
Family of R CrB stars
Model atmospheres & spectra vs opacities & H/He
CO in Sakurai's object
/ to be continued...