GCN Circular 3085
P.R. Wozniak, S. Evans, W.T. Vestrand, R. White, J. Wren (LANL) on behalf of the RAPTOR team. The RAPTOR A telescope responded to Swift-BAT trigger 107873 and began optical imaging of the burst location in 6.7 seconds from the time of receiving the alert (2.3 min. after GRB time). Photometry at the locations of the two X-ray candidate counterparts to GRB 050309 reported by Barthelmy et al. (GCN 3082) shows no optical emission in a series of 10 second exposures, each with the limiting magnitude R=15.0. A stack of the first 10 images with the mean time of observation 4.2 min. after the GRB time had a magnitude limit of R=16.1.