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 V = ( 660 - 1440 ) km \cdot 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 .