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arXiv · 0912.2118

The structure of AGNs from X-ray absorption variability

Guido Risaliti
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Abstract

We present new evidence of X-ray absorption variability on time scales from a few hours to a few days for several nearby bright AGNs. The observed N_H variations imply that the X-ray absorber is made of clouds eclipsing the X-ray source with velocities in excess of 10^3 km/s, and densities, sizes and distances from the central black hole typical of BLR clouds. We conclude that the variable X-ray absorption is due to the same clouds emitting the broad emission lines in the optical/UV. We then concentrate on the two highest signal-to-noise spectra of eclipses, discovered in two long observations of NGC 1365 and Mrk 766, and we show that the obscuring clouds have a cometary shape, with a high density head followed by a tail with decreasing N_H. Our results show that X-ray time resolved spectroscopy can be a powerful way to directly measure the physical and geometrical properties of BLR clouds.

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Guido Risaliti. 2009-12-10. The structure of AGNs from X-ray absorption variability. https://doi.org/10.1017/s1743921310006514

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