Cygnus X-1
Abstract
L. J. Kaluzienski, S. S. Holt, E. A. Boldt and P. J. Serlemitsos, Goddard Space Fliqht Center, report that a significant decrease (by at least a factor of two) in the 3-6 keV flux from Cyg X-1 has been detected by the Ariel 5 all-sky monitor. Cyg X-1 has been in a 'high state' since early Nov. 1975 (cf. IAUC 2863, 2879), during which the mean intensity on timescales of a few days has fluctuated between one and two times that of the Crab Nebula. The decline commenced around Feb. 19.0, and the source remained at or below this weaker level (0.6 times that of the Crab) until it disappeared from the instrument's field of view around Feb. 24.5. It is unclear at present whether the decrease signals a return to the 'low state' prior to Nov. 1975 or merely an extended low level during the current 'high state'.
- Publication:
-
International Astronomical Union Circular
- Pub Date:
- March 1976
- Bibcode:
- 1976IAUC.2918....3K