THE INFLUENCE OF MASS-LOSS ON THE OBSERVED X-RAY-SPECTRA OF EARLY-TYPE STARS

The observed X-ray spectra of early-type stars have been a major problem in the determination of the location of the emission source. The soft X-rays must propagate through a considerable column density of wind material, yet the Einstein Observatory Imaging Proportional Counter has seen no apparent signs of strong photoelectric absorption. We have investigated the photo-ionization state of such a wind and find that it is very sensitive to the mass loss rate. Acceptable spectra may be obtained from X-rays emitted at the base of the wind, where radiative efficiency is highest, for mass loss rates slightly lower than those inferred from UV, infrared and radio measurements. This provides further evidence for dumpiness of the wind material. Soft X-ray fluxes from five binary 0-stars are also presented. © Royal Astronomical Society.