On the role of relativistic effects in X-ray variability of AGN
  Special relativistic and strong gravity effects are clearly seen in X-ray energy spectra from AGN. Most important here are the broad profiles of the Fe Kalpha line observed in a large fraction of sources. These indicate that X-ray generation and reprocessing takes place very close to the central black hole. Here we explore consequences of such effects on X-ray variability. We perform computations of a possible quasi-periodic signal from a Keplerian motion of primary X-ray source. We also study in some details the light-bending model of variability of the X-ray reprocessed component, extending previous work on the subject. 
P. T. Zycki, A. Niedzwiecki