TITLE: GCN CIRCULAR NUMBER: 13883 SUBJECT: GRB 121017A: Swift/UVOT Upper Limits DATE: 12/10/18 11:31:14 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (MSSL-UCL) and D. Grupe (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 121017A 1142 s after the BAT trigger (Grupe et al., GCN Circ. 13875). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 13879) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 1142 1291 147 >21.1 white 1142 1442 167 >21.2 v 1298 1492 39 >18.5 b 1397 1417 19 >19.1 u 1373 1392 19 >18.6 w1 1347 1367 19 >18.1 w2 1448 1468 19 >18.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.44 in the direction of the burst (Schlegel et al. 1998).