EFFECTS OF CORONAL AND SHOCK-PRODUCED X-RAYS ON THE IONIZATION DISTRIBUTION IN HOT STAR WINDS

We investigate the effects of X-ray radiation on the ionization distri bution in the wind of zeta Pup (O4 If). In particular, we have studied how the distribution of the ''superionization'' species 0 VI is affec ted by X-ray source characteristics. In our calculations, detailed sta tistical equilibrium and atomic physics models are used to ensure that critical processes such as photoionization out of excited states and Auger ionization are considered. For shock-produced X-ray sources, we show how the distribution of X-ray emission affects the O VI P Cygni p rofile and the resultant X-ray spectrum. For coronal sources, we exami ne the sensitivity of the X-ray spectrum and O VI profile to the mass- loss rate and attenuation by the overlying wind. Results are compared with UV data from Copernicus and X-ray spectral data from the Einstein Imaging Proportional Center and Broad-Band X-ray Telescope. We find t hat coronal models are not simultaneously consistent with both UV and X-ray data unless the mass-loss rate is less than or similar to 1 x 10 (-6) M., yr-1, which is a factor of at least 3 to 5 lower than the val ues deduced from radio observations. Results from calculations using a mass-loss rate inferred from radio observations suggest that the X-ra y source is distributed throughout the wind. In addition, calculations using a distributed X-ray source indicate that a significant X-ray fl ux must originate from regions close to the star (within 2 stellar rad ii) in order to produce an O VI P Cygni profile consistent with observ ations.