PROFESSOR IOSSIF PAPADAKIS

The X-ray variations in AGN are well correlated at all energy bands, from 0.5 up to 10 keV. "Fourier time lags analysis" has demonstrated that the higher energy band variations are delayed with respect to the lower energy band variations, and that the delays decrease with increasing frequency. One of the more interesting results the last few years in the field of the AGN X-ray variability studies has been the detection of "soft lags" at high frequencies: in some sources, the soft band (ie ~ 0.2-1 keV) variations appear to be delayed with respect to the variations observed at higher energy bands (ie ~ 2-4 keV). It is widely believed that these results are due to "X-ray disc illumination", and they have been used to map the geometry on the innermost region in these objects. The speaker will review some of these results, and will discuss current work which aims to investigate the iron line lags with respect to the continuum.