BeppoSAX and Ulysses data on the giant flare from SGR 1900+14

The extraordinary giant flare of 1998 August 27 from SGR 1900+14 was the most intense event ever detected from this or any other cosmic source (even more intense than the famous 1979 March 5th event). 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 gamma-ray experiments in space, 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 data shows that the event emitted a strongly energy-dependent flux, and displayed strong spectral evolution during the outburst, itself. Here 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 ...