TITLE: GCN CIRCULAR NUMBER: 23336 SUBJECT: GRB 181013A: Swift/UVOT Upper Limits DATE: 18/10/14 00:31:04 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 181013A 106 s after the BAT trigger (D'Avanzo et al., GCN Circ. 23332). No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 23334) 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 867 1017 147 >20.2 u_FC 266 516 246 >19.1 white 867 1017 147 >20.2 u 266 516 246 >19.1 w1 818 7875 471 >20.4 m2 6035 7669 393 >19.6 w2 5624 7260 393 >20.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).