Circinus X-1
Abstract
L. J. Kaluzienski and S. S. Holt, Goddard Space Flight Center, report the detection of a peculiar flaring episode from Cir X-1 with the Ariel 5 all-sky monitor. The flare commenced on Jan. 15.35 +/- 0.04 UT and is characterized by a rapid turn-on (< 100 min), dip to the preflare flux level (~ 10 hours in duration) and subsequent recovery. The peak flux (3-6 keV) reached in the initial rise was approximately twice that of the Crab Nebula, more than an order of magnitude above the preceding quiescent level. Following the dip the intensity recovered to a level approximately equal to that of the Crab, and the source was still bright when last observed on Jan. T7. Based upon the latest available ephemeris and period (IAUC 3099), the observed time of the dip precedes the expected turn-off in the 16.6-day cycle by ~ 12 hours. This behavior differs distinctly from that exhibited by Cir X-1 during 1975-1977 and represents the first unambiguous detection of the source with the all-sky monitor since 1978 Feb. (IAUC 3171).
- Publication:
-
International Astronomical Union Circular
- Pub Date:
- January 1979
- Bibcode:
- 1979IAUC.3320....1K