The 1979 X-ray outburst of Cen X-4

Abstract

X-ray observations of the first major outburst (since its initial discovery in 1969) of the "classical" transient X-ray source Cen X-4 were obtained with the Ariel 5 All-Sky Monitor. The flare light curve exhibits a double-peaked maximum at a level of approximately 4 times the Crab nebula, and its duration and characteristic decay time scale are the shortest yet observed from the class of "soft" X-ray transients. A total X-ray output of approximately 3 x 10 to the 43rd power ergs, a factor of approximately 20 less than that of the 1969 outburst is estimated. In addition, evidence is found for a regular modulation of the flux during the decline phase at a period of 8.2 plus or minus 0.2 hours. The existing data are consistent with a source model involving episodic mass exchange from a late-type dwarf onto a neutron star comparison in a relatively close binary system