The effects of redshifts and focusing on the spectrum of an accretion disk around a Kerr black hole.
Abstract
The spectrum of X-rays produced by an accretion disk around a black hole is influenced markedly by Doppler shifls, gravitational red shifts, and the gravitational lens effect. These influences can be described by a "transfer function," which one folds into any assumed spectrum emitted on the disk's surface to get the spectrum observed at various locations far from the disk. This paper formulates such a transfer function and tabulates it for Kerr black holes of aIM = 0 and 0.9981. The transfer function depends strongly on the polar angle of the observer: An observer near the plane of the disk sees radiation from its hot inner regions to be less redshifted and to subtend a greater solid angle than does an observer near the disk's polar axis. Consequently, the equatorial observer sees a much harder spectrum at high energies than does the polar observer. This effect is more pronounced for black holes of larger angular momentum. Subject headings: black holes - gravitation - relativity - X-ray sources
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1975
- DOI:
- 10.1086/154033
- Bibcode:
- 1975ApJ...202..788C
- Keywords:
-
- Black Holes (Astronomy);
- Red Shift;
- Stellar Gravitation;
- X Ray Sources;
- X Ray Spectra;
- Angular Momentum;
- Astronomical Models;
- Doppler Effect;
- Mathematical Models;
- Relativistic Theory;
- Transfer Functions;
- Astrophysics