Intense X-ray flares from Aquila X-1 and Circinus X-1.
Abstract
Flare events have been observed by SAS 3 to emanate from Aql X- 1 (3U 1908+00) and Cir X- 1 (3U 1516-56). During 1975 June 3-8, the 1.5-6 keV intensity of Aql Xl increased by a factor of 20 to become equal to that of the Crab Nebula. The intensity then declined steadily by a factor of 7 over the next 30 days. On June 9, a search for periodicities in the range 1-500 5 yielded an upper limit of 3% (2 a) of the source intensity. A qualitatively different outburst was observed in Cir Xl which flared by a factor of 20 for only 2 days (1976 January 15-17) reaching an intensity of one-half that of the Crab Nebula in the energy range 1.5-6 keV. This large flare was preceded by a smaller one which also lasted 2 days. The intensity of Cir X-1 was observed to vary on time scales shorter than 1 5, as previously reported. These flare sources resemble transient X-ray sources and possibly differ only in the amplitude of their increases and the detectability of their quiescent intensities. Subject headings: X-rays: sources - X-rays: variable
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1977
- DOI:
- 10.1086/155102
- Bibcode:
- 1977ApJ...212..768B
- Keywords:
-
- Crab Nebula;
- Light Curve;
- Spaceborne Astronomy;
- Variable Stars;
- X Ray Sources;
- Ariel 5 Satellite;
- Flares;
- Luminous Intensity;
- Sas-3;
- Satellite Observation;
- X Ray Astronomy;
- X Ray Density Measurement;
- X Ray Stars;
- Astronomy