A Search for Gamma-Ray Transients in the Galactic Center Region with OSSE
Session 29 -- Gamma Ray Astrophysics
Oral presentation, Wednesday, January 12, 2:15-3:45, Salon III Room (Crystal Gateway)

## [29.09] A Search for Gamma-Ray Transients in the Galactic Center Region with OSSE

D.A. Grabelsky, S.M. Matz, W.R. Purcell, M.P. Ulmer (Northwestern University), W.N. Johnson, R.L. Kinzer, J.D. Kurfess, M.S. Strickman (Naval Research Lab), G.V. Jung (USRA)

The Oriented Scintillation Spectrometer Experiment on board the Compton Gamma Ray Observatory has carried out approximately 160 days of observations in the Galactic center region since the launch of the spacecraft in 1991 April. These observations represent a substantial data base for the study of transient gamma-ray line emission from the important central region of the Galaxy. Several experiments have reported such phenomena, but not all of them have had the extensive observing time in the Galactic center that OSSE has. In order to help determine whether or not this interesting behavior can be confirmed, we have undertaken a search of the OSSE Galactic center data for evidence of transient gamma-ray line sources on time scales much shorter than the ones used in our previous time-averaged analyses of these data.

The expected OSSE $3\sigma$ sensitivity to transient line emission in the .05--10 MeV range from the Galactic center is roughly .5--1 $\times 10^{-3} \ \gamma$ cm$^{-2}$ s$^{-1}$ for variability time scales from one day down to $\sim$ 5400 s (one CGRO orbit). The preliminary results of our search will be presented.