Radio Monitoring of the 1997 January 11 Gamma-Ray Burst

We report on a comprehensive radio monitoring program of the bright gamma-ray burster GRB 970111. These VLA observations were made at a frequency of 1.4 GHz (λ = 20 cm) and span a range of postburst timescales between 28 hr and 1 month. Despite extensive sampling at submillijansky sensitivities, no radio source was detected above 0.5 mJy in the current best error box (~14 arcmin 2 ) for GRB 970111. A highly unusual radio source, VLA J1528.7+1945, was seen to drop in flux density by a factor of 2 in our monitoring period, but it lies outside the error box, and thus it is unlikely to be related to GRB 970111. Cosmological fireball models of gamma-ray bursts make predictions of late-time emission occurring at longer wavelengths. The absence of a flaring or fading radio counterpart to GRB 970111 provides strong constraints on these models.