TITLE: GCN CIRCULAR NUMBER: 15160 SUBJECT: GRB 130831B: Swift/UVOT Upper Limits DATE: 13/09/01 17:28:26 GMT FROM: Frank Marshall at GSFC F.E. Marshall (NASA/GSFC) and D. Malesani (DARK/NBI) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 130831B 130 s after the BAT trigger (Malesani et al., GCN Circ. 15141). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 15149) 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 130 279 147 >20.3 u_FC 288 537 246 >19.6 white 130 6384 439 >20.9 v 618 5490 274 >19.7 b 543 6312 274 >20.5 u 288 6106 501 >20.3 w1 667 5901 274 >20.2 m2 642 5695 255 >20.9 w2 593 5285 274 >20.7 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.08 in the direction of the burst (Schlegel et al. 1998).