COLLIDING WINDS FROM EARLY-TYPE STARS IN BINARY-SYSTEMS

The collision of massive, supersonic stellar winds in early-type binary systems will produce a substantial flux of soft X-rays from the shock-heated material in the wind interaction region. In this paper we study the dynamics of the wind and shock structure formed by the wind collision. We employ a two-dimensional hydro-dynamics code, which self-consistently accounts for radiative cooling, and represents a significant improvement over previous attempts to model these systems. We calculate the X-ray luminosity and spectra of the shock-heated region, accounting for wind attenuation and the influence of different abundances on the resultant level and spectra of X-ray emission. We also examine a variety of dynamical instabilities that are found to dominate the intershock region. These instabilities are found to be particularly important when postshock material is able to cool. These instabilities disrupt the postshock flow and add a time variability of order 10% to the X-ray luminosity. The X-ray spectrum of these systems is found to vary with the nuclear abundances of the winds, which can be very nonsolar in the case of Wolf-Rayet stars. We use these theoretical models to study several massive binary systems, in particular V444 Cyg and HD 193793.