The giant flare of 1998 August 27 from SGR 1900+14 was extraordinary in many respects: it was the most intense event ever detected from this or any other cosmic source, it was longer than any previous burst from SGR1900+14 by more than one order of magnitude, and it displayed the same 5.16-s periodicity in hard X-rays that was detected in the low energy X-ray flux of its quiescent counterpart. The event was detected by several experiments, among them the Ulysses gamma-ray burst detector and the BeppoSAX Gamma Ray Burst Monitor. These instruments operate in different energy ranges, and a comparison of their their data shows that the event emitted a strongly energy- dependent flux, displaying strong spectral evolution during the outburst itself. We present a joint analysis of the BeppoSAX and Ulysses data, in order to identify the energy-dependent features of this event and understand some of the physical conditions in the environment of the neutron star which generated this flare. We compare it to newly analyzed data on the 1979 March 5 giant flare, and find some previously unknown similarities.
Fifth Huntsville Gamma Ray Burst Symposium
Hunsville, Alabama, USA
18-22 October, 1999