Hard X-ray observations of Circinus X-1 during an outburst
Abstract
WHILE the Ariel V satellite was observing in the Circinus-Norma region an outburst was detected from Cir X-1 on 1976 February 15 by the rotation modulation collimator (RMC) experiment1. One day before the outburst began the Imperial College hard X-ray scintillation telescope (ST) experiment (8° FWHM, 26 keV-1.2 MeV) completed a 4-d observation of this source and a strong signal was detected. For the following eight days, 1976 February 14-22, the source remained within the field of view, though at low sensitivity. Consequently only upper limits were obtained for the hard flux during the outburst and only a limited measure of the spectrum immediately afterwards. We have combined our results with the RMC results from reference 1 to obtain an overall view of the spectral behaviour of Cir X-1 during this outburst. We suggest that the large scale low energy X-ray outbursts of the `super-variable' Cir X-1 may be interpreted as corresponding to the periodic removal of a dense screening gas to expose a relatively stable source with a power law spectrum.
- Publication:
-
Nature
- Pub Date:
- August 1976
- DOI:
- 10.1038/262563a0
- Bibcode:
- 1976Natur.262..563C
- Keywords:
-
- Cosmic X Rays;
- Power Spectra;
- Radiant Flux Density;
- Spaceborne Astronomy;
- X Ray Sources;
- Ariel Satellites;
- Collimators;
- Photon Density;
- Scintillation Counters;
- Stellar Radiation;
- Astrophysics