title: A Transient Radio Source near the Center of the Milky Way Galaxy.
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.
authors.forename: J H
authors.initials: JH
authors.lastname: Zhao
authors.forename: D A
authors.initials: DA
authors.lastname: Roberts
authors.forename: W M
authors.initials: WM
authors.lastname: Goss
authors.forename: D A
authors.initials: DA
authors.lastname: Frail
authors.forename: K Y
authors.initials: KY
authors.lastname: Lo
authors.forename: R
authors.initials: R
authors.lastname: Subrahmanyan
authors.forename: M J
authors.initials: MJ
authors.lastname: Kesteven
authors.forename: R D
authors.initials: RD
authors.lastname: Ekers
authors.forename: D A
authors.initials: DA
authors.lastname: Allen
authors.forename: M G
authors.initials: MG
authors.lastname: Burton
authors.forename: J
authors.initials: J
authors.lastname: Spyromilio