On the Spectral Hardening Factor of the XRay Emission from Accretion Disks in Black Hole Candidates
Abstract
Radiation spectrum and the spectral hardening factor of an accretion disk around a Schwarzschild black hole with a mass of 1.4, 3, and 10 solar mass are determined by solving the vertical structure and radiative transfer selfconsistently. When a viscous parameter alpha is approximately 0.1, for accretion rates close to Eddington limit, the local spectrum can be described by the diluted blackbody spectrum with the spectral hardening factor f approximately 1.8  2.0 which is almost independent of a radial position and black hole mass. For approximately 10% of the Eddington rate, the local spectrum emitted from an inner region can be approximated by the diluted blackbody with f approximately 1.7. For accretion rates lower than 1% of the Eddington limit, the local spectrum cannot be fitted with any f. For accretion rates close to the Eddington limit, f increases with an increase of alpha in an inner region for alpha is greater than 0.1, and the radial dependence of f also becomes large gradually. We have applied our results to the observations of LMC X3, and have estimated the mass of the black hole in LMC X3 as greater than or equal to 7 solar mass.
 Publication:

The Astrophysical Journal
 Pub Date:
 June 1995
 DOI:
 10.1086/175740
 Bibcode:
 1995ApJ...445..780S
 Keywords:

 Accretion Disks;
 Black Holes (Astronomy);
 Mathematical Models;
 Radiative Transfer;
 X Ray Spectra;
 X Ray Stars;
 Active Galactic Nuclei;
 Black Body Radiation;
 Eddington Approximation;
 Emission Spectra;
 Schwarzschild Metric;
 Astrophysics;
 ACCRETION;
 ACCRETION DISKS;
 BLACK HOLE PHYSICS;
 RADIATIVE TRANSFER;
 XRAYS: STARS