TITLE: GCN CIRCULAR NUMBER: 9624 SUBJECT: GRB 090708: Early RAPTOR Optical Limits DATE: 09/07/08 20:31:21 GMT FROM: James Wren at LANL J. Wren, W.T. Vestrand, P.R. Wozniak, H. Davis, B. Norman of Los Alamos National Laboratory report: The RAPTOR telescope system responded to Swift trigger 356776 (Krimm et al., GCN 9621) under good observing conditions. A nearly full moon was above the horizon at the time of the observations, limiting sensitivity. Our narrow-field instruments began observing the location at 03:39:05.87 UTC, 50.62 s after the Swift trigger (6.9 s after receipt of GCN message). The data from our R-band filtered system was calibrated to the USNO-B1 catalog. These data show no new source within the BAT error circle (Palmer et al., GCN 9623) when compared to the DSS. We can put the following R-band (Cousins) limits on the emission: t-mid(s) exp(s) mag mag-err [since trigger] ---------------------------------------------------- 61.59 5.0 16.2 3 sigma limit 101.85 30.0 17.3 3 sigma limit