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THE DETERMINATION OF THE 'DIFFUSION COEFFICIENTS' AND
THE STELLAR WIND VELOCITIES FOR X-RAY BINARIES.
V.M.Lipunov 
and S.B.Popov 
Department of Physics, Moscow University, 119899, Moscow, Russia,
Sternberg Astronomical Institute,
Universitetsky pr., 13, Moscow, Russia
e-mail: lipunov@sai.msu.su and popov@sai.msu.su
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 accreting from a stellar wind, we determined the stellar wind velocity.
For different assumptions for a turbulent velocity we obtained
.
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.
Keywords: accretion:neutron stars-stars:stellar wind-stars.