Transient radio source near the center of the Milky Way Galaxy

Abstract

A new high-intensity radio source that appeared in late December 1990 near the center of the Galaxy is described. Following its first detection, the flux density of this Galactic-center transient (GCT) increased rapidly to a maximum a month later, and then declined gradually during the next 3 months. However, throughout its rising and decay phases, the GCT maintained a steep radio spectrum. Neutral-hydrogen-absorption and OH observations indicate that the GCT is either embedded in, or located behind, a molecular cloud moving with the velocity of +20 km/sec with respect to the local standard of rest. It is suggested that the GCT represents a transient radio emission from synchrotron-radiating plasma associated with an X-ray binary system