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Pair-density transitions in accretion disk coronaeThe thermal and e(+)e(-)-pair equilibrium structure of two-temperature disk coronae above a cool (about 10 exp 6 K) disk around a black hole of 10 solar masses are investigated. Soft photons are assumed to be amply supplied from the cool disk. Two-pair thermal equilibrium points are found for a given proton column density: the low state with very small pair density and the high state dominated by pairs. Both states are thermally unstable, while for perturbations in pair density the high state is unstable and the low state is stable. Two possible scenarios are discussed for the fate of a two-temperature corona. When the proton optical depth is relatively small (e.g., less than 1) and the temperature of input soft photons is low (e.g., less than 10 exp 6 K), the corona will undergo a limit cycle between the high state and the low state on a time scale of milliseconds. As a consequence of Compton scattering of the soft photons, the emergent spectrum in the high state is rather flat with a big Wien bump at about 100 keV, whereas it is composed of a power-law component in the low state. Some observational consequences are briefly discussed in connection with the high-low spectral transition in Cyg X-1.
Document ID
19920030091
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Kusunose, Masaaki
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Mineshige, Shin
(Cambridge, University England; Ibaraki University, Mito, Japan)
Date Acquired
August 15, 2013
Publication Date
November 10, 1991
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 381
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
92A12715
Distribution Limits
Public
Copyright
Other

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