Abstract

The optical transient of the faint gamma-ray burst GRB 990308 was detected by the QUEST camera on the Venezuelan 1 m Schmidt telescope starting 3.28 hr after the burst. Our photometry gives V = 18.32 +/- 0.07, R = 18.14 +/- 0.06, B = 18.65 +/- 0.23, and R = 18.22 +/- 0.05 for times ranging from 3.28 to 3.47 hr after the burst. The colors correspond to a spectral slope of close to f(v) proportional to nu(1/3). Within the standard synchrotron fireball model, this requires that the external medium be less dense than 10(4) cm(-3), the electrons contain more than 20% of the shock energy, and the magnetic field energy be less than 24% of the energy in the electrons for normal interstellar or circumstellar densities. We also report upper limits of V> 12.0 at 132 s (with LOTIS), V > 13.4 from 132 to 1029 s (with LOTIS), V>15.3 at 28.2 minutes (with Super-LOTIS), and a 8.5 GHz flux of less than 114 mu Jy at 110 days (with the Very Large Array). Wisconsin-Indiana-Yale-NOAO 3.5 m and Keck 10 m telescopes reveal this location to be empty of any host galaxy to R > 25.7 and K> 23.3. The lack of a host galaxy likely implies that it is either substantially subluminous or more distant than a redshift of similar to 1.2.