EUV/X-ray Emission and the Thermal and Ionization Structure of B Star Winds

Abstract

We discuss the EUV and X-ray properties of B stars, focusing on $ε$ CMa (B2 II) which is the only star with both emission lines and a photospheric continuum detected with EUVE. We explore the modest effects of the photospheric EUV continua on the wind, as well as the much stronger effects of the short-wavelength EUV and soft X-ray emission lines. Attenuation of the EUV and soft X-ray emission by the wind plays an important role, and leads to the reprocessing of X-rays via He$^+$ ionization and the Bowen mechanism in the wind. Finally, we explore some of the new diagnostics that will shortly become available with the next generation of high spectral resolution X-ray telescopes. All of this analysis is presented in the context of a two component stellar wind--a dense component (clumps) that contains most of the mass but fills a negligible fraction of the volume, and a rarefied component that fills most of the volume but accounts for only a small fraction of the mass.