2000/05/31 by Sergei Nayakshin, Nayakshin, Sergei
Physics and Astronomy · #Astrophysics (astro-ph) #Astrophysics and Cosmic Phenomena #FOS: Physical sciences #Gamma-ray bursts and supernovae #Solar and Space Plasma Dynamics #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0005603
submitted to ApJL on May 31 2000; 4 pages, 2 figures
arxiv created 2000/05/31 · openalex publication_date 2000/05/31 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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 \em 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.