NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Variability of accretion disks surrounding black holes: The role of inertial-acoustic mode instabilitiesThe global nonlinear time-dependent evolution of the inertial-acoustic mode instability in accretion disks surrounding black holes has been investigated. The viscous stress is assumed to be proportional to the gas pressure only, i.e., tau = alphap(sub g). It is found that an oscillatory nonsteady behavior exists in the inner regions of disks (r is less than 10r(sub g) where r(sub g) is the Schwarzschild radius) for sufficiently large alpha(greater than or approximately equal to 0.2) and for mass accretion rates less than about 0.3 times the Eddington value. The variations of the integrated bolometric luminosity from the disk, Delta L/L, are less than 3%. A power spectrum analysis of these variations reveals a power spectrum which can be fitted to a power-law function of the frequency Pis proportional to f(exp -gamma), with index gamma = 1.4-2.3 and a low-frequency feature at about 4 Hz in one case. In addition, a narrow peak centered at a frequency corresponding to the maximum epicyclic frequency of the disk at approximately 100-130 Hz and its first harmonic is also seen. The low-frequency modulations are remarkably similar to those observed in black hole candidate systems. The possible existence of a scattering corona in the inner region of the disk and/or other processes contributing to the power at high frequencies in the inner region of the accretion disk may make the detection of the high-frequency component difficult.
Document ID
19950044581
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Chen, Xingming
(Univ of Goteborg and Chalmers Univ of Technology Goteborg, Sweden)
Taam, Ronald E.
(Northwestern University Evanston, IL, United States)
Date Acquired
August 16, 2013
Publication Date
March 1, 1995
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 441
Issue: 1
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A76180
Funding Number(s)
CONTRACT_GRANT: NAGW-2526
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available