Variability Spectra of Orbiting Blobs around a Black Hole
Abstract
Variability power spectra of the distribution of orbiting blobs in an optically thick accretion disk around a black hole are investigated by a full relativistic approach. Both the well-known α disks and β disks are considered. The calculations also include the cases when the emitting matter is optically thin or optically thick. The resulting variability spectra are characterized by a power-law shape with flattening frequency at its lower end and a drop-off frequency at its higher end, both corresponding to the borders of blobs distribution in the disk. The frequencies are intrinsic to all sources with an inhomogeneous accretion disk around a black hole, independent of either the specific property of the disk or the nature of the blobs. The drop- off frequency could be an important clue in determining the mass of the central black hole if the distribution of the blobs extends to the last stable circular orbit around a black hole. It may also be taken as evidence for the relativistic rotation of accretion disks around the hole. The average slopes of the observed X-ray power spectra are around -1.5 for both active galactic nuclei and Galactic black hole candidates, suggesting the number density distribution n(r) is proportional to rdelta^ with 0 <= δ <= 1. This may improve our understanding of fluctuations of accretion disks.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1995
- DOI:
- 10.1086/175502
- Bibcode:
- 1995ApJ...443...54B
- Keywords:
-
- Accretion Disks;
- Black Holes (Astronomy);
- Clumps;
- Power Spectra;
- Relativistic Effects;
- Variability;
- Active Galactic Nuclei;
- Astronomical Models;
- Density Distribution;
- Frequency Ranges;
- Optical Thickness;
- Astrophysics;
- ACCRETION;
- ACCRETION DISKS;
- BLACK HOLE PHYSICS;
- GALAXIES: NUCLEI