The effects of redshifts and focusing on the spectrum of an accretion disk around a Kerr black hole
The spectrum of X-rays produced by an accretion disk around a black hole is influenced markedly by Doppler shifts, gravitational redshifts, 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 a/M=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 reshifted 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. (AIP)
- Research Organization:
- California Institute of Technology, Pasadena
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-33-024030
- OSTI ID:
- 4050486
- Journal Information:
- Astrophys. J., v. 202, no. 3, pp. 788-802, Other Information: Orig. Receipt Date: 30-JUN-76
- Country of Publication:
- United States
- Language:
- English
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