Anomalous diffusion in the dynamics of X-ray emission of astrophysical objects

Abstract

We use the anomalous-diffusion interpolation and parameterization procedure developed within the framework of flicker-noise spectroscopy (FNS) to characterize the stochastic variability of X-ray emission from accreting black hole GRS 1915+105. Our analysis of the lightcurves with a sampling frequency of 16 Hz in soft and hard X-ray energy bands shows that the stochastic variability of soft-band lightcurves is mostly subdiffusive while the hard X-ray emission is characterized primarily by fractional Gaussian noise. The comparison of FNS parameters between the soft and hard energy bands (corresponding roughly to different X-ray emission mechanisms) implies that hard X-rays have more relative variability at higher frequencies and are characterized by shorter diffusion timescales than soft X-rays. We suggest that the differences in the stochastic variabilities may be attributed to changes in either the viscosity law in the accretion disk or the geometry of the accretion flow.