TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5645 SUBJECT: GRB 060926: Swift-UVOT UVW1 Detection Retraction DATE: 06/09/28 14:57:57 GMT FROM: Pete Roming at PSU P. Roming (PSU) and S. T. Holland (GSFC/USRA) report on behalf of the Swift-UVOT team: Due to an error in the flux calculation, the reported UVW1 (251 nm) filter detection in GCN 5625 is not real. No optical afterglow is detected at the 3-sigma level in individual or coadded exposures in this filter. The 3-sigma limiting magnitude for the coadded images is listed below: Filter T_range(s) Exp(s) Upper Limit (3-sigma) UVW1 487-11748 1337 20.4 where T_range is the start and end times of the coadded exposures. No correction has been made for Galactic reddening along the line of sight (E(B-V) = 0.16). We also point out that the 4.8-sigma level V-filter detection report in GCN 5625 is real. We apologize for any inconvenience this error has created.