TITLE: GCN CIRCULAR NUMBER: 13839 SUBJECT: GRB 121001A: Swift/UVOT Upper Limits DATE: 12/10/02 17:12:45 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) and V. D'Elia (ASDC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 121001A 130 s after the BAT trigger (D'Elia et al., GCN Circ. 13831). No optical afterglow consistent with the optical position (Tello et al. GCN Circ. 13835) 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) exposures and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 130 280 147 >21.0 u_FC 288 538 246 >20.0 white 130 7415 824 >22.4 v 618 6390 352 >20.2 b 544 7210 526 >21.2 u 288 7005 756 >20.7 w1 668 6800 529 >20.4 w2 767 7608 439 >21.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.36 in the direction of the burst (Schlegel et al. 1998).