Real-Time Optical Flux Limits From Gamma-Ray Bursts Measured By The GROCSE Experiment

The Gamma-Ray Optical Counterpart Search Experiment (GROCSE) 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 (BACODINE). The experiment acquired 3800 observing hours, recording 22 gamma-ray burst triggers within $\sim 30 s$ 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 amongst these events at the $m_V \sim 7.0 to 8.5$ sensitivity level. We find the ratio of the upper limit to the V-band optical flux, $F_\nu$, to the gamma-ray fluence, $\Phi_\gamma$, from these data to be $2 \times 10^{-18} < F_\nu/\Phi_\gamma < 2 \times 10^{-16}$.