TITLE: GCN CIRCULAR NUMBER: 23498 SUBJECT: GRB 181202A: Swift/UVOT Detection DATE: 18/12/04 00:09:57 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and J. K. Cannizzo (NASA/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 181202A 86 s after the BAT trigger (Cannizzo et al., GCN Circ. 23482). A source consistent with the XRT position (Evans et al. GCN Circ. 23483) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 18:42:56.38 = 280.73491 (deg.) Dec (J2000) = +27:57:35.0 = 27.95971 (deg.) with an estimated uncertainty of 0.47 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag v 623 1540 117 >18.7 b 342 591 246 19.57 +/- 0.18 u (fc) 86 336 246 17.67 +/- 0.07 w1 672 1441 97 >19.6 m2 647 1560 112 >22.2 w2 598 1516 117 >20.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.14 in the direction of the burst (Schlegel et al. 1998).