THERMAL EQUILIBRIA OF OPTICALLY THIN, MAGNETICALLY SUPPORTED, TWO-TEMPERATURE, BLACK HOLE ACCRETION DISKS

Journal Article · Sat Mar 20 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/712/1/639· OSTI ID:21394242

Oda, H ^[1]; Machida, M ^[2]; Nakamura, K E ^[3]; Matsumoto, R ^[4]

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
2. Department of Physics and Astrophysics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan)
3. Department of Sciences, Matsue National College of Technology, 14-4 Nishiikuma-cho, Matsue, Shimane 690-8515 (Japan)
4. Department of Physics, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)

We obtained thermal equilibrium solutions for optically thin, two-temperature black hole accretion disks incorporating magnetic fields. The main objective of this study is to explain the bright/hard state observed during the bright/slow transition of galactic black hole candidates. We assume that the energy transfer from ions to electrons occurs via Coulomb collisions. Bremsstrahlung, synchrotron, and inverse Compton scattering are considered as the radiative cooling processes. In order to complete the set of basic equations, we specify the magnetic flux advection rate instead of beta = p{sub gas}/p{sub mag}. We find magnetically supported (low-beta), thermally stable solutions. In these solutions, the total amount of the heating via the dissipation of turbulent magnetic fields goes into electrons and balances the radiative cooling. The low-beta solutions extend to high mass accretion rates ({approx}>alpha{sup 2}M-dot{sub Edd}) and the electron temperature is moderately cool (T{sub e} {approx} 10{sup 8}-10{sup 9.5} K). High luminosities ({approx}>0.1L{sub Edd}) and moderately high energy cutoffs in the X-ray spectrum ({approx}50-200 keV) observed in the bright/hard state can be explained by the low-beta solutions.

• OSTI ID: 21394242
• Journal Information: Astrophysical Journal, Vol. 712, Issue 1; Other Information: DOI: 10.1088/0004-637X/712/1/639; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
ADVECTION
BALANCES
BLACK HOLES
BREMSSTRAHLUNG
COMPTON EFFECT
ELECTRON TEMPERATURE
ELECTRONS
ENERGY TRANSFER
EQUATIONS
LUMINOSITY
MAGNETIC FIELDS
MAGNETIC FLUX
MATHEMATICAL SOLUTIONS
RADIATIVE COOLING
THERMAL EQUILIBRIUM
X RADIATION
X-RAY SPECTRA
BASIC INTERACTIONS
COOLING
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
EQUILIBRIUM
FERMIONS
INTERACTIONS
IONIZING RADIATIONS
LEPTONS
MASS TRANSFER
MEASURING INSTRUMENTS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SCATTERING
SPECTRA
WEIGHT INDICATORS