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Preprint typeset using L ATEX style emulateapj v. 04/03/99 IONIZATION PHYSICS EVIDENCE FOR MAGNETIC FLARE ORIGIN OF THE X-RAYS IN AGN

By Sergei Nayakshin

Abstract

We present full disk X-ray reflection spectra for two currently popular accretion flow geometries for AGN – the lamppost model frequently used to discuss the iron line reverberation in AGN, and the model where the X-rays are produced in magnetic flares above a cold accretion disk (AD). The lamppost spectra contain several spectroscopic features characteristic of highly ionized material that are not seen in the X-ray spectra of most AGN. The magnetic flare model, on the other hand, produces reflected spectra that are roughly a super-position of a power-law and a neutral-like reflection and iron Kα line, and are thus more in line with typical AGN X-ray spectra. Furthermore, because of the difference in the ionization structure of the illuminated material in the two models, the line equivalent width increases with the X-ray luminosity, Lx, for the lamppost, and decreases with Lx for the flare model. In light of these theoretical insights, recent iron line reverberation studies of AGN, the X-ray Baldwin effect, and the general lack of X-ray reflection features in distant quasars all suggest that, for high accretion rates, the cold accretion disk is covered by a Thomson thick, completely ionized skin. Because the latter is only possible when the X-rays are concentrated to small emitting regions, we believe that this presents a strong evidence for the magnetic flare origin of X-rays in AGN. Subject headings: accretion, accretion disks —radiative transfer — line: formation — X-rays: genera

Year: 2008
OAI identifier: oai:CiteSeerX.psu:10.1.1.317.6499
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