AAS 197, January 2001
Session 80. HEAD Contributions: Pulsars to X-ray Clusters
Display, Wednesday, January 10, 2001, 9:30am-7:00pm, Exhibit Hall

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[80.08] Estimation of relativistic accretion disk parameters from iron line emission

V.I. Pariev (Los Alamos National Laboratory; University of Arizona), B.C. Bromley (University of Utah), W.A. Miller (Los Alamos National Laboratory)

The observed iron K-alpha fluorescence lines in Seyfert-1 galaxies provide strong evidence for an accretion disk near a supermassive black hole as a source of the emission. Here we present an analysis of the geometrical and kinematic properties of the disk based on the extreme frequency shifts of a line profile as determined by measurable flux in both the red and blue wings. The edges of the line are insensitive to the distribution of the X-ray flux over the disk, and hence provide a robust alternative to profile fitting of disk parameters. Our approach yields new, strong bounds on the inclination angle of the disk and the location of the emitting region. We apply our method to interpret observational data from MCG-6-30-15 and find that the commonly assumed inclination 30 degrees for the accretion disk in MCG-6-30-15 is inconsistent with the position of the blue edge of the line at a 3 sigma level. A thick turbulent disk model or the presence of highly ionized iron may reconcile the bounds on inclination from the line edges with the full line profile fits based on simple, geometrically thin disk models. The bounds on the innermost radius of disk emission indicate that the black hole in MCG-6-30-15 is rotating faster than 30~% of theoretical maximum. When applied to data from NGC~4151, our method gives bounds on the inclination angle of the X-ray emitting inner disk of 50±10 degrees, consistent with the presence of an ionization cone grazing the disk as proposed by Pedlar et al. (1993). The frequency extrema analysis also provides limits to the innermost disk radius in another Seyfert-1 galaxy, NGC~3516.

The author(s) of this abstract have provided an email address for comments about the abstract: vpariev@lanl.gov

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