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Academy of Sciences of the Czech Republic |
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Academy of Sciences of the Czech Republic |
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Public lecture November 14, 2005
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Monday November 14, 2005 in the lecture room in Cosmic Laboratory Ondrejov Modeling time-dependent X-ray spectra of magnetic flares in the vicinity of accreting supermassive black holes René GoosmannObservatoire Paris-Meudon Active Galactic Nuclei (AGN) release a significant fraction of their bolometric luminosity in the X-ray band. These X-rays appear to be strongly variable with flux variations by a factor of 2-3 within 1 hour. A promising model to explain this extreme behavior is suggested by assuming X-ray flares above an accretion disk. These flares should originate from magnetic reconnection events, similar to what is observed during solar flares. During my talk, I present radiative transfer modeling of the X-ray emission from magnetic compact flares in AGN. In this model, the hard X-ray primary radiation coming directly from the flare source illuminates the accretion disk, which is supposed to stay in hydrostatic equilibrium. A Compton reflection/reprocessed component coming from the disk surface is computed for several flare locations and for different emission directions. This modeling takes into account the variations of the incident radiation across the hot-spot underneath the flare source. Time-dependent spectra and light curves for orbiting flares at various distances from the black hole are computed using a full general relativity ray tracing technique. The computations are carried out for black holes of different masses and accretion rates. Rms-variability spectra for large flare distributions across the disk are also computed and compared to observed X-ray data of the Seyfert-1 galaxy MCG-6-30-15. Vladimir Karas organizer |