Effect of an electron scattering cloud on X-ray oscillations produced by beaming

The effect of a scattering cloud on the amplitude of oscillations produced by a rotating beam of X-rays is investigated using analytical and Monte Carlo methods. The scattering cloud was modeled as a uniform density sphere, and the source was represented as an anistropic distribution of radiation emerging from a point at the center of the scattering cloud. The intensity distribution produced by the source beam is examined as a function of optical depth. The relation between electron scattering optical depth and the forward-backward ratio is studied. It is observed that the scattering in a central corona of various optical depths reduces the amplitude of the oscillation. The data suggest that the quasi-periodic oscillations observed in the X-ray intensities of some luminous low-mass X-ray binaries are caused by oscillations in the luminosity of the X-ray star.