Energy spectrum and the absolute flux of various celestial X-ray sources

Abstract

The results on the flux of low energy X-rays in the range 2–18 Kev from Sco-X1, Tau-X1 and Cen-X2 celestial sources observed during two rocket flights, flown from the Thumba Equatorial Rocket Launching Station (TERLS), Trivandrum, India, are presented. The absolute flux and the energy spectrum obtained for these sources are compared with other similar observations. The results indicate a long-term exponential decrease in the energy flux of X-rays from Sco-X1 over the period 1965–1968. The X-ray source Cen-X2, which showed a remarkable outburst of X-rays in April 1967, had ceased to be active after May 1967. We present here the first evidence of the rediscovery of the low energy, X-ray flux from Cen-X2 since May 1967. These short-lived X-ray out-bursts may be attributed to a shock wave from the nova outburst expanding into the circumstellar medium.