Modelling the energy dependencies of X-ray quasi-periodic oscillations in accreting compact objects.

Abstract

We have constructed models of the quasi-periodic variability of X-ray emission from accreting compact objects. Assuming a general scenario of a propagation model of variability, with inverse Compton upscattering as the emission mechanism, we have considered a number of cases for the periodic modulation: modulation of the plasma heating rate, cooling rate by external soft photons and the amplitude of the reprocessed component. We have computed various observational characteristics which can be compared to good quality data. These include Fourier-frequency resolved spectra and the results of cross-correlation analysis between light curves at different energies. Each model of modulation predicts specific observational signatures, which help in identifying the physical processes driving quasi-periodic oscillations emission in accreting sources.