Observations of the Circinus X-1 region.
Abstract
The X-ray telescope on board the OSO-7 satellite has provided observations of the Cir X-1 region for over 110 days between December 1971 and March 1973. Although statistically significant fluctuations in the 7- to 11-keV flux were measured, no periodicities in the range between 5 hours and 100 days were found to an upper limit of about 40 percent amplitude. Intensities in the 7- to 57-keV range show variability by a factor of approximately 25 and changes in the spectral shape reflected by a number spectral index varying from about 1.1 to about 3.0. There is a positive correlation between intensity and spectral shape, with a steeper spectrum at times of peak intensity. Although power-law, exponential, and blackbody spectral shapes are equally good fits to these data alone, examination of all the available data appears to rule out a simple blackbody spectrum, at least at times of maximum intensity.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 1975
- DOI:
- 10.1086/153621
- Bibcode:
- 1975ApJ...198..447B
- Keywords:
-
- Energy Spectra;
- Stellar Spectra;
- X Ray Sources;
- Astronomical Maps;
- Oso-7;
- Photons;
- Spaceborne Telescopes;
- Astronomy