TITLE: GCN CIRCULAR NUMBER: 8654 SUBJECT: GRB 081210: Swift/UVOT refined analysis DATE: 08/12/11 18:59:03 GMT FROM: Stefan Immler at NASA/GSFC S. Immler (CRESST/UMD/GSFC), S. T. Holland (CRESST/USRA/GSFC), and H. A. Krimm (CRESST/GSFC/USRA) report on behalf of the Swift UVOT team: Further analysis of Swift Ultraviolet/Optical Telescope (UVOT) data of GRB 081210 (Krimm et al., GCN Circ. 8648), starting 80 sec after the BAT trigger, gives a detection of an optical source consistent with the enhanced XRT position (Osborne et al., GCN Circ 8650) in the white and u filters at 12.6-sigma and 3.8-sigma levels of confidence, respectively. The source is not detected in any of the other UVOT filters at the limiting magnitudes reported below. Filter Tstart(s) Tstop(s) Exp(s) Magnitude wh 80 1009 318 19.91+/-0.08 u 292 716 265 20.15+/-0.29 b 548 741 39 >19.78 (3-sigma UL) uvw2 598 5251 235 >20.47 (3-sigma UL) v 622 816 244 >19.99 (3-sigma UL) uvm2 647 840 136 >19.55 (3-sigma UL) uvw1 672 866 39 >18.74 (3-sigma UL) The values quoted above are in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) and are not corrected for the expected Galactic extinction along the line of sight which corresponds to a reddening of E(B-V) = 0.077 mag (Schlegel et al. 1998). The event data in the white filter shows a flare peaking at approximately 130 s after the BAT trigger, which approximately coincides with the flare seen in the X-ray light curve (Evans et al., GCN Circ 8652).