The annihilation line source at the Galactic Center turns on.
01 January 1989
A new balloon-borne germanium telescope has been flown twice in 1988 over Alice Springs, Australia to study gamma-ray line and continuum emission from the Galactic Center (GC) direction. The 511 keV positron annihilation line was detected at a flux level of (9.8 +- 1.9) x 10 sup (-4) gamma cm sup (-2) s sup (-1) on 1 May 1988 and (12.3 +- 1.6) x 10 sup (-4) gamma cm sup (-2) s sup (-1) on 28 October 1988. Apparently after being quiescent in the early 1980's, the compact object has re-emerged sometime between 1984 and 1988.