TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4136 SUBJECT: GRB051021: Swift/UVOT Upper Limits DATE: 05/10/22 17:01:06 GMT FROM: Peter Brown at PSU P. J. Brown (PSU), D. Fox (PSU), M. Trippico (GSFC-SSAI), J. Nousek (PSU), & N. Gehrels (GSFC) on behalf of the Swift/UVOT team report: The Swift-UVOT began observing the field of GRB 051021 (HETE Trigger H3947; Yoshida et al. GCN 4116) at 2005-10-21 16:28:27, about 3 hours after the burst. No source is detected at the position of the optical counterpart found by Fox, McNaught, & Peterson (GCN 4120) in any of our 6 filters down to the following 3-sigma upper limits: Filter T_range(hours) Exp(sec) 3sigUL V 3.36-8.34 1988 20.2 B 5.30-6.71 1304 21.1 U 5.04-5.29 900 20.5 W1 4.79-5.04 900 20.8 M2 3.61-3.80 900 20.9 W2 3.11-6.96 1800 21.7 Where T_range is time post-trigger.