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Hot Accretion Disks with Magnetic Field and Thermal Cyclo-Synchrotron Radiation

Published online by Cambridge University Press:  19 July 2016

Masaaki Kusunose
Affiliation:
Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland
Andrzej A. Zdziarski
Affiliation:
Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland

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We study the structure of hot, two-temperature accretion disks around black holes, including the effects of thermal cyclo-synchrotron radiation and magnetic viscosity. This work is an extension of previous work by Björnsson & Svensson (1991a, b, 1992) and Kusunose & Mineshige (1992), which did not include those effects. Magnetic field, B, is assumed to be randomly oriented and determined by prescribing the ratio α = P mag/P gas or α = P mag/(P gas + P rad), where P mag, P gas, and P rad are the pressures of magnetic field, gas, and radiation, respectively. We find those effects do not change the qualitative properties of the disks, i.e., there are two critical accretion rates related to production of e ± pairs, cr U and cr L that affect the number of local and global disk solutions, as recently found for the case with B = 0 (Björnsson & Svensson 1991a, b, 1992). However, a critical value of the α-viscosity parameter above which those critical accretion rates disappear becomes smaller than αcr = 1 found in the case of B = 0, for P mag = α(P gas + P rad). If P mag = αP gas, on the other hand, αcr is still about unity. Moreover, when Comptonized cyclo-synchrotron radiation dominates Comptonized bremsstrahlung, radiation from the disk obeys a power law with the energy spectral index of ∼ 0.5, in a qualitative agreement with X-ray observations of AGNs and Galactic black hole candidates. The spectral index is weakly dependent on the mass accretion rate.

Type
Poster Contributions: Disks Structure and Emission
Copyright
Copyright © Kluwer 1994 

References

Björnsson, G., & Svensson, R. 1991a, in Structure and Emission Properties of Accretion Disks (IAU Colloq. 129), ed. Bertout, C., Collin, S., Lasota, J.-P., & Van, J. Tran Thanh (Gif-sur-Yvette: Éditions Frontières), 379 Google Scholar
Björnsson, G., & Svensson, R. 1991b, in Relativistic Hadrons in Cosmic Compact Objects, ed. Zdziarski, A. A. & Sikora, M. (Berlin: Springer), 53 CrossRefGoogle Scholar
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