Constraining the beaming of gamma-ray bursts with radio surveys

The degree of beaming in gamma-ray bursts (GRBs) is currently unknown. The uncertainty in the gamma-ray-beaming angle, theta(b), leaves the total ener gy release (proportional to theta(b)(2)) and the event rate per galaxy (pro portional to theta(b)(-2)) unknown to within orders of magnitude. Since the delayed radio emission of GRB sources originates from a mildly relativisti c shock and receives only weak relativistic beaming, the rate of radio-sele cted transients with no GRB counterparts can be used to set an upper limit on theta(b)(-2). We find that a VLA survey with a sensitivity of similar to 0.1 mJy at 10 GHz could identify greater than or similar to 2 x 10(4) (the ta(b)/10 degrees)(-2) radio afterglows across the sky if each source is sam pled at least twice over a period of 1 month or longer. From the total numb er of greater than or similar to 0.1 mJy sources observed at 8.44 GHz and t he fraction of fading sources at 1.44 GHz, we get the crude limit theta(b) greater than or similar to 6 degrees.