TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3603 SUBJECT: GRB050713B :Swift/UVOT observations DATE: 05/07/13 22:17:04 GMT FROM: Simon Rosen at MSSL-UCL S. Rosen (MSSL), S. Vaughan (Leicester), R. Fink (GSFC-SPSYS), M. Chester (PSU) report on behalf of the Swift UVOT team: Using summed images from Swift/UVOT of the field of GRB 050713B, taken from 136 seconds after the BAT trigger, no new source is detected within the XRT error circle (Vaughan et al., GCN 3590) in any of the six filters down to the following 3-sigma magnitude upper limits: Filter Exposure (s) T_mid (s) 3-sig limit V 252 598 19.26 B 88 624 19.58 U 88 610 19.31 UVW1 88 596 19.46 UVM2 88 582 19.83 UVW2 88 639 19.87 where T_mid is the mid-point of the summed observation. We caution that the instrument is not yet fully calibrated and that the magnitude limits presented here may need to be refined.