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The Structure of AGNs from X-Ray Absorption Variability

Published online by Cambridge University Press:  03 June 2010

Guido Risaliti
Guido Risaliti*
Affiliation:
INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, Firenze, Italy Email: [email protected] Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
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Abstract

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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 NH variations imply that the X-ray absorber is made of clouds eclipsing the X-ray source with velocities in excess of 103 km s−1, 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 NH. 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.

Keywords

galaxies: activegalaxies: SeyfertX-rays: galaxiesX-ray: individual (NGC 1365, Mrk 766)
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S267: Co-Evolution of Central Black Holes and Galaxies , August 2009 , pp. 299 - 306
Copyright
Copyright © International Astronomical Union 2010

References

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