Kavli Affiliate: Erin Kara
| First 5 Authors: Christos Panagiotou, Iossif Papadakis, Erin Kara, Elias Kammoun, Michal Dovčiak
| Summary:
The UV/optical variability of AGN has long been thought to be driven by the
X-ray illumination of the accretion disk. However, recent multi-wavelength
campaigns of nearby Seyfert galaxies seem to challenge this paradigm, with an
apparent discrepancy between observations and the underlying theory. In order
to further probe the connection between the UV/optical and X-ray variability in
AGN we developed a physical model to reproduce the UV/optical power spectra
(PSDs) of AGN assuming the thermal reprocessing of the X-rays in the disk. This
model offers a novel way to probe the innermost regions of AGN. We use our
model to study the variability of NGC 5548 and we infer that the X-ray and
UV/optical PSDs as well as the interband UV/optical time lags are all well
reproduced. We also derive constraints on the source physical parameters, such
as the X-ray corona height and the accretion rate. Our results suggest that
X-ray disk reprocessing accounts for the full variability properties of this
AGN, within the considered time scales. Using earlier data of NGC 5548, we also
show that our model can reproduce its PSD in different epochs, establishing the
feasibility of using PSD modelling to investigate the time evolution of a
source.
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