0 A pr 1 99 5 THE DETERMINATION OF THE ’ DIFFUSION COEFFICIENTS ’ AND THE STELLAR WIND VELOCITIES FOR X – RAY BINARIES

The distribution of neutron stars (NS's) is determined by stationary solution of the Fokker–Planck equation. In this work using the observed period changes for four systems: Vela X–1, GX 301–2, Her X–1 and Cen X–3 we determined D, the 'diffusion coefficient',– parameter from the Fokker–Planck equation. Using strong dependence of D on the velocity for Vela X–1 and GX 301–2, systems ac-creting from a stellar wind, we determined the stellar wind velocity. For different assumptions for a turbulent velocity we obtained V = (660 − 1440) km · s −1. It is in good agreement with the stellar wind velocity determined by other methods. We also determined the specific characteristic time scales for the 'diffusion processes' in X-ray pulsars. It is of order of 200 sec for wind-fed pulsars and 1000-10000 sec for the disk accreting systems.