Broadband, time-dependent, spectroscopy of the brightest bursts observed by BATSE LAD and EGRET TASC

Official URL: http://dx.doi.org/10.1088/0004-637X/696/2/2155

The Energetic Gamma Ray Experiment Telescope (EGRET) calorimeter, Total Absorption ShowerCounter (TASC), was triggered by the Burst And Transient Source Experiment (BATSE) and thus observed several bursts in the energy range of 1-200 MeV. The analysis of combined BATSE Large Area Detector and EGRET TASC data have been developed and discussed previously. Spectroscopy of GRB941017 based on this analysis uncovered an MeV component that would be hidden in the brightness of the synchrotron component in a time-integrated spectrum of the whole burst, while separation into shorter time intervals allowed a unique identification of a new component different from the synchrotron component. In this paper the spectral temporal evolution of the 68 brightest long BATSE bursts, in the broadest energy range yet reported, is studied using the analysis used for GRB941017. We consider the Band function to describe the spectra from keV to MeV energies. Only 21 of the 68 bursts showed MeV emission detectable by TASC. We observed three bursts that contained spectra with peak energy E-peak > 2 MeV.