BATSE observations of the very intense gamma-ray burst GRB 930131

Abstract

BATSE observed its most intense gamma-ray burst on 1993 January 31. The event reached count rates >~ 2 x 10^6 counts/s with most o fthe flux emitted in an extremely short ( 4 MeV in energy were recorded by BATSE during this first interval. The burst spectrum is best fitted by a broken power law with a break energy of 170 +/ 27 keV. The low-energy spectral index is -1.30 +/- 0.05, while a softer spectral index of -1.9 fits the spectrum between 170 keV and 2 MeV. Our data provide the only low-energy spectrum for this event; the combination of our spectrum with the one reported for GRB 930131 by the EGRET group extends the total energy spectrum of a GRB for the first time over five decades, up to the GeV range.