TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3516 SUBJECT: GRB050603: Fading Afterglow observed by Swift UVOT DATE: 05/06/03 21:21:19 GMT FROM: Patricia Schady at MSSL/Swift P. Brown (PSU), A. Retter (PSU), P. Schady (MSSL), P. Roming (PSU), C. Gromwall (PSU), N. Cucchiara (PSU), P. Boyd (GSFC), K. Mason (MSSL), N. Gehrels (GSFC), on behalf of the Swift UVOT team The Swift Ultra-Violet/Optical Telescope (UVOT) began observations of GRB050603 on June 3, 2005 at 15:42:59 UT, ~9 hours after the initial Swift BAT trigger (Retter et al, GCN 3509). The observations were delayed because automated slewing was not enabled during engineering tests at the time of the burst. A fading source is detected in the V band at the afterglow position first reported by Berger & McWilliam (GCN 3511). The coordinates of this source are Ra, Dec = 02:39:56.839, -25:10:54.92 Astrometry was performed using reference stars from the GSC. Magnitudes from the two long exposures are as follows: Filter Magnitude Duration(s) T_start(s) V 18.2 +/- 0.12 1298 32997 V 21.8 +/- 0.4 2103 38782