Gamma-ray astronomy

Abstract:

We present a brief discussion of high resolution observations of relativistic ejections from GRS 1915+103 with MERLIN. We have imaged superluminal motions in the inner 300 milliarcsec of several ejections from the system, with significantly higher proper motions than previously observed on arcsecond scales with the VLA. Under standard assumptions of an intrinsically symmetric jet, we derive a velocity for the ejecta which is higher then the previously accepted value of 0.92c, although the angle to the line of sight is comparable. © 1999 OPA (Overseas Publishers Association) N.V Published by license under the Gordon and Breach Science Publishers imprint.

Abstract:

GX 339-4 is an unusual black hole candidate in that it is a persistent source, being detected by X-ray telescopes most of the time, but it also has nova-like flaring states. In 1996 we performed radio, optical, X-ray, and gamma-ray observations of GX 339-4 when it was in a hard state (= soft X-ray low state). Here we present a brief summary of some of the results. © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.

Abstract:

Cyg X-3 is an unusual X-ray binary which shows remarkable correlative behavior between the hard X-ray, soft X-ray, and the radio. We present an analysis of these long term light curves in the context of spectral changes of the system. This analysis also incorporates a set of pointed RXTE observations made during a period when Cyg X-3 made a transition from a flaring state (including a major flare) to a quiescent radio state. © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.