The structure of AGNs from X-ray absorption variability

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.

8 Pages, 5 figures. Proceedings of IAU Symposium 267 "Co-Evolution of Central Black Holes and Galaxies"

References in corpus (4)

• Occultation measurement of the size of the X-ray emitting region in the Active Galactic Nucleus of NGC 1365
• Variable partial covering and a relativistic iron line in NGC 1365
• Rapid N_H changes in NGC 4151
• How complex is the obscuration in AGN? New clues from the Suzaku monitoring of the X-ray absorbers in NGC7582