Stability of accretion disks around black holes
A stability analysis of the accretion process around a black hole is presented within the context of a thin alpha-disk model. The analysis includes azimuthal as well as radial perturbations. All terms resulting from the dispersion relation are retained, making this study more complete than previous analysis. For the purely radial analysis, a viscous and a thermal instability arise in the inner region of the accretion disk. A phase velocity is present over all radial perturbation wavelengths and, contrary to Shakura and Sunyaev (1976), pure standing waves do not result. The viscous instability is found to arise only in the purely radial mode. When azimuthal perturbations are included, the thermal instability behaves radially like a standing wave upon which is superposed an azimuthal mode with constant phase velocity. Hot spots may therefore develop, whose Keplerian rotation may account for the rapid fluctuations observed from accreting systems. Due to the inherent shearing of the hot spots, a duration time of the oscillations is predicted. The results are applied to several types of accreting objects where this analysis is thought to be relevant, such as the galactic black hole candidate source Cyg X-1, active galactic nuclei, and non-magnetic neutron star systems.
- Research Organization:
- Pennsylvania State Univ., University Park (USA)
- OSTI ID:
- 5413642
- Country of Publication:
- United States
- Language:
- English
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