paper

On the origin of the Fe K-alpha line cores in Active Galactic Nuclei

arXiv:astro-ph/0602081 · doi:10.1111/j.1745-3933.2006.00158.x

Abstract

X-ray observations with Chandra and XMM-Newton have shown that there are relatively narrow cores to the iron K-alpha emission lines in active galactic nuclei (AGN). Plausible origins for this core emission include the outer regions of an accretion disk, a pc-scale molecular torus, and the optical broad-line region (BLR). Using data from the literature it is shown that no correlation exists between the Fe K-alpha core width and the BLR (specifically H-beta) line width. This shows that in general the iron K-alpha core emission does not arise from the BLR. There is a similar lack of correlation between the width of the Fe K-alpha core and black hole mass. The average K-alpha width is about a factor of two lower than the H-beta width. It therefore seems likely that in many cases the narrow core arises in the torus. There is a very wide range of observed Fe K-alpha core widths, however, and this argues for multiple origins. The simplest explanation for the observed line profiles in AGN is that they are due to a mixing of very narrow emission from the inner edge of the torus, and broadened emission from the accretion disk, in varying proportions from object-to-object.

arXiv comment5 pages, 2 figures, accepted for publication in MNRAS Letters

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