Superlow-state hard X-ray observation of Cygnus X-1
- CNR, Istituto di Astrofisica Spaziale, Frascati (Italy) CNR, Istituto di Fisica Cosmica, Milan (Italy) Southampton Univ. (England)
Hard-X-ray observations of Cyg X-1, obtained using the multiwire proportional counters and scintillator arrays of the Milan-Frascati-Southampton balloon-borne instrument package during July 1987, are reported. The results are combined with previous observational data and presented in tables and graphs. A very low flux similar to that measured by the HEAO-3 gamma-ray spectrometer in 1979 and in agreement with low-energy observations by the Ginga satellite during August 1987 is detected, confirming that the object is in a superlow state. The photon spectrum is found to be well fit by a Comptonized model with electron temperature 56 keV and optical depth 2.3, or by a simple power law with photon index alpha = 1.92 and intensity 1.10 crab. 32 refs.
- OSTI ID:
- 5994957
- Journal Information:
- Astrophysical Journal; (USA), Vol. 366; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
BINARY STARS
HARD X RADIATION
BLACK HOLES
COSMIC X-RAY SOURCES
ELECTRON TEMPERATURE
GAMMA RADIATION
GRAPHS
TABLES
X-RAY SPECTRA
COSMIC RAY SOURCES
ELECTROMAGNETIC RADIATION
IONIZING RADIATIONS
RADIATIONS
SPECTRA
STARS
X RADIATION
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources