Search for optical emission from cosmic gamma-ray bursts

Long-exposure films are available for both times and regions of sky for several cosmic gamma-ray bursts. A visual magnitude of no more than 6 was set for optical emission from the well-observed May 14, 1972, event. The corresponding lower limit for the ratio of X-ray to optical energy flux in the burst is greater than 100. This may restrict solar-flare analogy models for the burst sources.