Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 1989
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989apj...343..313b&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 343, Aug. 1, 1989, p. 313-316.
Astronomy and Astrophysics
Astronomy
10
Black Holes (Astronomy), Gamma Ray Astronomy, X Ray Binaries, Compton Effect, Cygnus Constellation, Gamma Ray Spectra, Heao 3, Pair Production, X Ray Spectra
Scientific paper
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.
Bassani Loredana
Dean Anthony J.
Di Cocco Guido
Perotti Federico
Stephen John B.
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