Returning radiation in accretion disks around black holes.
Abstract
Returning radiation is radiation emitted by an accretion disk which returns to its surface due to gravitational focusing or the shape of the disk. While it is unimportant for thin disks around nonrotating black holes, returning radiation will have significant effects on the structure and appearance of thin disks around rotating holes with a/M 1. We calculate the flux of the returning radiation as a function of radius for aIM = 0.9, 0.99, 0.9981, and 0.9999, treating the propagation of the radiation by general-relativistic geometric optics and treating the disk as thin. We also consider the effects of returning radiation on the spectrum of an accretion disk seen by a distant observer. The spectrum will be modified by the returning radiation at photon energies greater than about 10 keV and less than about 10 eV. The notch at 10 keV in the "pre-transition" spectrum of Cyg X- 1 might be a "signature" of returning radiation. Subject headings: black holes - X-rays: sources
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1976
- DOI:
- 10.1086/154636
- Bibcode:
- 1976ApJ...208..534C