TITLE: GCN CIRCULAR NUMBER: 12000 SUBJECT: GRB 110503A: Swift/UVOT Observations DATE: 11/05/04 10:58:36 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) & M. Stamatikos (OSU/NASA/GSFC) report on behalf of the Swift-UVOT team The Swift/UVOT began settled observations of the field of GRB 110503A 212s after the trigger (Stamatikos et al., GCN Circ. 11991). We detect a fading source in all filters at a refined position of RA(J2000), DEC(J2000)= 132.77588 deg,52.20767 deg. This is equivalent to: RA (J2000) 8:51:06.21 Dec (J2000) 52:12:27.6 with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence). This is consistent with the UVOT position reported in Stamatikos et al. (GCN Circ. 11991) and with the enhanced position of the X-ray afterglow (Goad et al., GCN Circ. 11992). Preliminary magnitudes using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the finding chart (FC) and summed exposures at the location of the optical afterglow are: Filter T_start(s) T_stop(s) Exp(s) Mag ##################################################### wh (FC) 212 362 147 15.82 +/- 0.02 wh 864 1014 147 17.09 +/- 0.03 v 368 388 20 16.23 +/- 0.14 b 469 488 19 16.79 +/- 0.10 u 445 464 19 15.87 +/- 0.09 uvw1 419 438 19 16.15 +/- 0.15 uvm2 394 414 19 17.27 +/- 0.32 uvw2 519 539 19 17.72 +/- 0.31 ##################################################### The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).