ON DETERMINING THE WIND VELOCITY PROFILES OF EARLY-TYPE STARS IN MASSIVE X-RAY BINARY-SYSTEMS

We discuss the determination of stellar wind velocity profiles for OB stars by means of modelling the variable X-ray absorbing column seen in massive X-ray binary systems. The orbital variability in the column density profiles in eclipsing systems, such as Vela X-1 or 4U1700 - 37, provides an excellent opportunity for determining the wind velocity laws of OB stars in general. We consider the types of velocity laws that have been assumed in the previous modelling of such systems, and point out an important potential flaw in much of the previous work which probably precludes any detailed comparison of these results with theoretical wind models. We suggest improvements which should enable future wind modelling work to confront theoretical models in a useful manner, as we are investigating features of the wind dynamics that are specific to binary systems, such as tidal streams and X-ray ionization effects.