TITLE: GCN CIRCULAR NUMBER: 10922 SUBJECT: Swift/UVOT observations of GRB100702A DATE: 10/07/02 13:37:35 GMT FROM: Massimiliano de Pasquale at MSSL-UCL M. De Pasquale (MSSL-UCL) and M. H. Siegel (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 100621A 101s after the BAT trigger (Siegel et al, GCN 10916). The enhanced XRT error circle appears crowded with sources (Malesani et al., GCN 10918, Fong et al, GCN 10919) which blend together. There is no clear indication of change of optical flux between the first exposures and later ones. The preliminary magnitudes and 3-sigma upper limits for the finding chart exposures (FC) and summed images for the emission in the XRT enhanced error circle are: Filter T_start T_stop Exp(s) Magnitude/3-sigma upper limit ------------------------------------------------------------- white (FC) 101 251 147 17.99 +/- 0.07 white 594 10684 1295 17.84 +/- 0.05 u (FC) 314 564 246 18.85 +/- 0.17 u 5020 5151 131 18.96 +/- 0.26 v 4405 17014 735 16.72 +/- 0.04 b 570 6306 216 17.79 +/- 0.08 uvw1 4815 5015 196 > 19.60 uvm2 4610 4810 197 > 19.40 uvw2 4200 16457 1432 > 20.85 ------------------------------------------------------------- The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to E_(B-V) = 0.41 mag. All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).