A transient radio source near the center of the Milky Way Galaxy

Zhao, Jun-Hui ; Roberts, D. A. ; Goss, W. M. ; Frail, D. A. ; Lo, K. Y. ; Subrahmanyan, R. ; Kesteven, M. J. ; Ekeres, R. D. ; Allen, D. A. ; Burton, M. G. ; Spyromilio, J. (1992) A transient radio source near the center of the Milky Way Galaxy Science, 255 (5051). pp. 1538-1543. ISSN 0036-8075

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Official URL: http://science.sciencemag.org/content/255/5051/153...

Related URL: http://dx.doi.org/10.1126/science.255.5051.1538


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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