December 11, 1997 CfA Colloquium

Title: Gamma Ray Bursts: Dying Cries from the Deep Universe

Speaker: Shri Kulkarni, Cal Tech

Abstract: A few times a day the sky is lit up by brilliant flashes of gamma-rays. This phenomenon was discovered about three decades ago. Yet till recently astronomers knew very little about the nature of these sources. The bursters appear to be isotropic and yet inhomogeneously distributed around us. This required the bursters to be either local to our Galaxy or at cosmological distances. The speaker will present evidence that decisively demonstrate that at least one burster is located at a cosmological distance. These bursts are then the most brilliant astronomical objects -- so-called fireballs. In addition, the speaker will present observations of several of these fireballs including the measurement of their size and super-luminal expansion and deceleration. The cause or origin of the bursts are unknown but widely speculated to be the death of some kind of stars.

Reference for students: Get from Jean Collins "Unsolved Problems in Astrophysics" by Bahcall and Ostriker, GRBs chapter.