Zhao JH, Roberts DA, Goss WM, Frail DA, Lo KY, Subrahmanyan R, Kesteven MJ, Ekers RD, Allen DA, Burton MG, Spyromilio J. A Transient Radio Source near the Center of the Milky Way Galaxy.
Science 1992;
255:1538-43. [PMID:
17820165 DOI:
10.1126/science.255.5051.1538]
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Abstract
In late December 1990, a new radio source appeared near the center of our galaxy rivaling the intensity of Sgr A(*) (the compact radio source at the galactic center). Following its first detection, the flux density of the galactic center transient (GCT) increased rapidly to a maximum 1 month later, and then declined gradually with a time scale of about 3 months. Surprisingly, the GCT maintained a steep radio spectrum during both its rising and decay phases. The neutral hydrogen (HI) absorption shows similar absorption to that in front of Sgr A(*); this indicates that the GCT lies near the galactic center. Furthermore, both HI and OH observations show an additional deep absorption at +20 kilometers per second with respect to the local standard of rest. Thus, the GCT is either embedded in or located behind a molecular cloud moving with that velocity. The cloud can be seen on infrared images. Its opacity is shown to be inadequate to conceal a supernova near the galactic center. It is argued that the GCT was probably transient radio emission from synchrotron-radiating plasma associated with an x-ray binary system.
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