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An X-ray Baldwin effect for the narrow Fe K-alpha lines observed in Active Galactic Nuclei

K. L. Page·P. T. O'Brien·J. N. Reeves·M. J. L. Turner
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Abstract

The majority of Active Galactic Nuclei (AGN) observed by XMM-Newton reveal narrow Fe K-alpha lines at ~ 6.4 keV, due to emission from cold (neutral) material. There is an X-ray Baldwin effect in Type I AGN, in that the equivalent width of the line decreases with increasing luminosity, with weighted linear regression giving EW ~ L^{-0.17+/-0.08} (Spearman Rank probability of > 99.9%). With current instrumental capabilities it is not possible to determine the precise origin for the narrow line, with both the Broad Line Region and putative molecular torus being possibilities. A possible explanation for the X-ray Baldwin effect is a decrease in covering factor of the material forming the fluorescence line.

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K. L. Page, P. T. O'Brien, J. N. Reeves, M. J. L. Turner. 2003-09-15. An X-ray Baldwin effect for the narrow Fe K-alpha lines observed in Active Galactic Nuclei. https://doi.org/10.1111/j.1365-2966.2004.07203.x

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