Real‐Time Optical Flux Limits from Gamma‐Ray Bursts Measured by the Gamma‐Ray Optical Counterpart Search Experiment

Abstract

The Gamma-Ray Optical Counterpart Search Experiment presents new experimental upper limits on the optical flux from gamma-ray bursts (GRBs). Our experiment consisted of a fully automated very wide-field opto-electronic detection system that imaged locations of GRBs within a few seconds of receiving trigger signals provided by BATSE's real-time burst coordinate distribution network. The experiment acquired 3800 observing hours, recording 22 gamma-ray burst triggers within ~30 s of the start of the burst event. Some of these bursts were imaged while gamma-ray radiation was being detected by BATSE. We identified no optical counterparts associated with gamma-ray bursts among these events at the m_V ~ 7.0-8.3 sensitivity level. We find the ratio of the upper limit to the V-band optical flux, F_ν, to the gamma-ray fluence, Φ_γ, from these data to be 1 × 10^-18 < F_ν/Φ_γ < 2 × 10^-16.