Comptonization of X radiation in a plasma of accreting neutron stars

Basing on diffusion approximation, the continuum radiative transfer problem is considered for optically thick homogeneous nonrelativistic plasma where incoherent Compton scattering is important, as it occurs in Z-ray-emitting neutron stars (NS). The hypothesis on the Compton origin of the Cyg X-1 low-state spectrum leads also to the constraint Ne<or approx.1018 cm-3 in the inner hot region of the accretion disk surrounding a black hole. The simplified approach is suggested for allowance for the stimulated scattering effects which permits to avoid difficulties concerning the nonlinear transfer equation numerical solution. The results are useful in data interpretation and in the consideration of realistic models of the NS radiating regions