24 May 2010
Iosif Papadakis (U Crete)
'On the X-ray variability of Type 1, radio-quiet Seyferts'
The X-ray variability properties of AGN have been extensively
studied during the past twenty years. Significant progress has
been achieved in the estimation of their X-ray power spectral
density functions (PSDs), which (among other things) can be helpful in
the search for characteristic time scales in these objects.I will
present a review of recent results which have shown that the PSDs
have a -2 power law shape at high frequencies and then, below a
characteristic "break - frequency" it flattens to a slope of -1. The
corresponding "break timescale", increases with increasing black hole
mass, and for a given mass, it decreases with increasing accretion rate.
I will discuss the constrains that these relationships put on the
characteristic time scales associated with the the accretion process
itself, which fuels the emission in these objects. I will also present
evidence which indicate a relationship between the PSD characteristic
time scales and the energy spectral slope in AGN, and I will discuss
possible implications of this relationship.