The Structure of AGNs from X-Ray Absorption Variability

AbstractWe 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.

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Measuring the supermassive black hole parameters with space missions

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307006023 ◽

2006 ◽

Vol 2 (S238) ◽

pp. 475-476

Author(s):

Alexander F. Zakharov

Keyword(s):

Black Hole ◽

Spectral Line ◽

Accretion Disks ◽

Seyfert Galaxies ◽

Emission Lines ◽

X Ray ◽

Line Shapes ◽

Supermassive Black Hole ◽

Broad Emission ◽

Different Types

AbstractRecent X-ray observations of microquasars and Seyfert galaxies reveal broad emission lines in their spectra, which can arise in the innermost parts of accretion disks. Recently Müller & Camenzind (2004) classified different types of spectral line shapes and described their origin. Zakharov (2006b) clarified their conclusions about an origin of doubled peaked and double horned line shapes in the framework of a radiating annulus model and discussed s possibility to evaluate black hole parameters analyzing spectral line shapes.

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Bardeen-Petterson Effect and Broad HI Profiles of Seyferts

Symposium - International Astronomical Union ◽

10.1017/s0074180900162175 ◽

1999 ◽

Vol 194 ◽

pp. 313-316

Author(s):

Rumen Bachev

Keyword(s):

Black Hole ◽

Accretion Disk ◽

Rotation Axis ◽

Kerr Black Hole ◽

Orbital Plane ◽

Emission Lines ◽

Planar Structure ◽

X Ray ◽

Broad Emission ◽

Schwarzschild Radius

A thin accretion disk could be not only the energy source of AGN but also the matter producing broad emission lines of Seyfert 1 type nuclei (Dumont & Collin-Souffrin, 1990 B). A possible mechanism for this is reprocessing of central hard X-ray radiation by the outer (at 102–5 RG, RG is the Schwarzschild radius), low-temperature regions of the disk. This mechanism is effective enough especially if the disk is a non-planar structure (a warped or twisted disk), when the outer parts could be directly seen from the centre. An accretion disk around a Kerr black hole could be twisted if the angular momentum of the accreting gas is initially not aligned with the rotation axis of the hole. Due to the differential Lense-Thirring precession of orbits around a Kerr black hole, a viscous disk is a steady but non-planar structure. This is the well-known Bardeen-Petterson effect (Bardeen & Petterson, 1975). Near the hole, at distances R>RBP, where RBP is the Bardeen-Petterson radius, the flow is aligned with the equatorial plane of the black hole, while at larger distances it is tilted to its initial orbital plane (Fig. 1).

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