Extrapolations of BATSE Gamma-Ray Burst Spectra to the Optical-UV Band

Abstract

Many gamma-ray burst counterpart searches are being conducted in the optical-UV band. To both predict detectability and understand the meaning of any detections or upper limits, we extrapolate gamma-ray spectra from 54 bright gamma-ray bursts to optical-UV energies. We assume optical emission is concurrent with gamma-ray emission and do not consider quiescent or fading counterparts. We find that the spectrum must be steeper (greater flux at low energy) than a simple extrapolation of the gamma-ray spectrum for more than one simultaneous optical flash to be observable per year by current searches.