M.I.T. studies of transient X-ray phenomena

A variety of transient X-ray phenomena have been studied by the M.I.T. X-ray Astronomy Group. Data from the OSO-7 satellite reveal both long and short time-scale transients. Extensive observations have been made of the Lupus X-ray Nova (3U1543-47) and of GX339-4 (MX1658-48) which may represent a very different type of transient source A unique, intense X-ray flare lasting ten minutes was also recorded, and the X-ray emission from the active galaxy Cen A was found to vary significantly over a period of several days. In a recent ballon flight the Crab, pulsar, NP0532, was observed to exhibit a transient pulsed component distinct from the usual main pulse and interpulse. A sounding-rocket experiment detected an ultrasoft transient X-ray source tentatively associated with SS Cygni, and preliminary results from SAS-3 show a very hard spectrum for the new source A0535+26. On the other hand, extensive OSO-7 null observations of both Type I and II supernovae and of the flaring radio star Algol make it unlikely that these types of objects are potent transient X-ray emitters.Supported in part by the National Aeronautics and Space Administration under contracts NGL 22-009-015, NSR 22-009-654 and grant NGL 22-099-730 and by the National Science Foundation under grant GP-31378.Paper presented, at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.