Implications of light metals (Li−Ca) on NLTE model atmospheres for hot stars

Abstract

Neither iron line-blanketed LTE model atmospheres nor “standard” NLTE models (including H, He, C, N, O, Ne) can reproduce the observed stellar EUV and X-ray fluxes of hot stars: huge differences appear at energies higher than 54 eV (He II Lyman continuum) which are a result of light metal opacities which have a strong influence on the emergent fluxes of hot stars in this energy range. These metal opacities have not been included in “standard” NLTE model atmosphere calculations so far. We present NLTE model atmospheres including all elements from hydrogen to calcium.

In order to calculate more realistic stellar fluxes, such models should preferentially be used for the EUV and X-ray analysis of very hot stars instead of black bodies which are often used in the analysis of X-ray spectra.