Limits on prompt radio emission from GRB 950430 and GRB 950706 at 151 MHz

Abstract

The Cambridge Low Frequency Synthesis Telescope (CLFST) has been used to search for prompt radio emission at 151 MHz from gamma-ray bursts. To make the best use of the trigger information from the BACODINE system, the CLFST has been reconfigured so that it can reach ∼10 per cent of the sky in 1.5 minutes. Observations of GRB 950430 and GRB 950706 made in this mode are presented here. These provide deep upper limits on the flux density of any radio pulse matching the GRB duration. Assuming a thermal radio spectrum, these results yield an upper limit of a few times 10−4 for the ratio of the radio to the gamma-ray luminosity for periods of several hours before, during and after GRB 950430, and about an hour shortly after GRB 950706.