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Hard X-ray spectrum of Cygnus X-1Long-term measurements of the hard X-ray spectrum from 3 keV to 8 MeV of the black-hole candidate Cygnus X-1 in its low state are reported. Observations were made from October 26 to November 18, 1977 with the A2 (Cosmic X-ray) and A4 (Hard X-ray and Low-Energy Gamma-Ray) experiments on board HEAO 1 in the spacecraft's scanning mode. The measured spectrum below 200 keV is found to agree well with previous spectra which have been fit by a model of the Compton scattering of optical or UV photons in a very hot plasma of electron temperature 32.4 keV and optical depth 3.9 or 1.6 for spherical or disk geometry, respectively. At energies above 300 keV, however, flux excess is observed which may be accounted for by a distribution of electron temperatures from 15 to about 100 keV.
Document ID
19810064515
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Nolan, P. L.
(California Univ. La Jolla, CA, United States)
Gruber, D. E.
(California Univ. La Jolla, CA, United States)
Knight, F. K.
(California Univ. La Jolla, CA, United States)
Matteson, J. L.
(California Univ. La Jolla, CA, United States)
Rothschild, R. E.
(California, University La Jolla, CA, United States)
Marshall, F. E.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Levine, A. M.
(California Univ. La Jolla, CA, United States)
Primini, F. A.
(MIT Cambridge, MA, United States)
Date Acquired
August 11, 2013
Publication Date
September 24, 1981
Publication Information
Publication: Nature
Volume: 293
Subject Category
Astrophysics
Accession Number
81A48919
Funding Number(s)
CONTRACT_GRANT: NAS8-27974
Distribution Limits
Public
Copyright
Other

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