Non-LTE line-blanketed model atmospheres of hot stars. 2: Hot, metal-rich white dwarfs

Details Non-LTE line-blanketed model atmospheres of hot stars. 2: Hot, metal-rich white dwarfs Non-LTE line-blanketed model atmospheres of hot stars. 2: Hot, metal-rich white dwarfs

Feb 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...439..905l&link_type=abstract

The Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 439, no. 2, p. 905-916

Astronomy and Astrophysics

Astrophysics

73

Abundance, Atmospheric Models, Local Thermodynamic Equilibrium, Metallic Stars, Stellar Atmospheres, Stellar Models, White Dwarf Stars, Carbon, Equilibrium Equations, Hydrogen, Hydrostatics, Iron, Line Spectra, Metallicity, Radiative Transfer

Scientific paper

We present several model atmospheres for a typical hot metal-rich DA white dwarf, Teff = 60,000 K, log g = 7.5. We consider pure hydrogen models, as well as models with various abundances of two typical 'trace' elements-carbon and iron. We calculte a number of Local Thermodynamic Equilibrium (LTE) and non-LTE models, taking into account the effect of numerous lines of these elements on the atmospheric structure. We demostrate that while the non-LTE effects are not very significant for pure hydrogen models, except for describing correctly the central emission in H-alpha they are essential for predicting correctly the ionization balance of metals, such as carbon and iron. Previously reported discrepancies in LTE abundances determinations using C III and C IV lines are easily explained by non-LTE effects. We show that if the iron abundance is larger than 10-5, the iron line opacity has to be considered not only for the spectrum synthesis, but also in the model construction itself. For such metal abundances, non-LTE metal line-blanketed models are needed for detailed abundance studies of hot, metal-rich white dwarfs. We also discuss the predicted Extreme Ultraviolet (EUV) spectrum and show that it is very sensitive to metal abundances, as well as to non-LTE effects.

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