Gamma-Ray Observations of Cygnus X-1
Abstract
The results of gamma-ray observations of the Galactic black hole candidate Cygnus X-1 are presented. The recent HEAO 3 results reported by Ling et al. (1987) on this source are confirmed: (1) the detection in 1979 of a gamma-ray excess of comparable flux; and (2) a spectral variation above about 25 keV going from 1979 to 1980, which implies and anticorrelation between hard X-ray and gamma-ray luminosities with a pivot point in the 200-400 keV band. A comparison of all the data available at gamma-ray energies gives further support to the existence of this anticorrelation, although its statistical significance is low. The hard X-ray/gamma-ray 1979 spectrum, which is well fitted by a power law with photon index alpha = 1.7, can be interpreted as thermal Comptonization of soft photons or in terms of nonthermal models with copious photon-photon absorption.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1989
- DOI:
- 10.1086/167705
- Bibcode:
- 1989ApJ...343..313B
- Keywords:
-
- Black Holes (Astronomy);
- Gamma Ray Astronomy;
- X Ray Binaries;
- Compton Effect;
- Cygnus Constellation;
- Gamma Ray Spectra;
- Heao 3;
- Pair Production;
- X Ray Spectra;
- Astrophysics;
- GAMMA RAYS: GENERAL;
- RADIATION MECHANISMS;
- STARS: INDIVIDUAL CONSTELLATION NAME: CYGNUS X-1;
- X-RAYS: BINARIES