Searching for prompt GRB counterparts at 74 MHz

The Fallbrook Low-Frequency Immediate Response Telescope (FLIRT) is an experiment designed to detect prompt radio counterparts to gamma ray bursts (GRBs) at 74 MHz. FLIRT is notified of GRBs by the BACODINE and radio observations begin as early as one minute after the detection of a GRB. The goal of FLIRT is to detect radio counterparts to GRBs and measure their distances by measuring the dispersion of the radio bursts. The dispersion of a radio signal is a function of the source’s distance from earth and its galactic coordinates. Radio emission at 74 MHz which was emitted coincident with the GRB at the source would be observed to follow a GRB by 15 s≲δt≲30 min with galactic GRBs producing shorter delays and cosmological GRBs producing longer delays. Our 1.6 MHz bandwidth is divided into four frequency channels to allow direct measurement of the dispersion across our band. The dispersion measure calculated across the radio bandwidth can then be compared to the dispersion measure implied by the time delay ...