RUNAWAY INSTABILITY AND GAMMA-RAY BURSTS

We re-investigate the global runaway instability of massive (self-grav itating) tori around black holes. For the first time, the metric and e quipotentials have been computed fully relativistically from the Einst ein field equations. We find that the instability exists in the few mo dels that we have constructed. The runaway instability may provide the shortest evolutionary time-scale relevant for the current model of ga mma-ray bursts based on the merger of neutron star binaries. Our rough estimate, based on the linear analysis of the stability of stationary tori, gives the time-scale for the lifetime of such tori, Delta t(T) much less than 1s.