PROFESSOR IOSSIF PAPADAKIS

The speaker will present an overview of the X-ray flux and spectral variability studies of AGN in the last two decades. He will focus on results obtained by the use of power-spectral analysis of long RXTE and XMM light curves. The AGN X-ray power spectra show a "break" frequency, where the power spectral slope steepens. The "break" frequency scales with black hole mass, and may also scale with the source's accretion rate. He will present some results from recent work regarding the physical interpretation of these results. He will also discuss the energy dependence of the AGN X-ray power spectra, and the constrains they pose on the nature of the X-ray source in AGN.