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

Journal Article · Sat Mar 20 04:00:00 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, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 712; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

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