GCN Circular 10368
R.L.C. Starling (U Leicester), E.A. Hoversten (PSU) and F.E. Marshall (NASA/GSFC) report on behalf of the Swift XRT and UVOT teams: We observed the Swift GRB 100203A, detected in ground analysis (Cummings et al. GCN Circ. 10360), with Swift XRT and UVOT beginning 25.66 hours (92.3 ks) after the BAT trigger (#411011). The XRT observed the field for 3.85 ks. No source has been detected at the 3-sigma confidence level or above, with a 3-sigma upper limit on the count rate at the BAT position of 6 x 10^-3 ct s^-1. We note that this source lies near the Galactic Plane, where Galactic absorption in this direction is high, at 5.3 x 10^21 cm^-2. The UVOT observed the field of GRB 100203A in the uvm2 filter. Visual comparison with DSS images of the field reveal no afterglow candidates. Given the low Galactic latitude, afterglow detection is complicated by high extinction and numerous bright stars in the field. The observed 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for initial exposures are: Filter T_start(s) T_stop(s) Exp(s) 3-sigma upper limit ============================================================= uvm2 92604 103268 3915 > 21.27 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.55 in the direction of the burst (Schlegel et al. 1998). This circular is an official product of the Swift team.