TITLE: GCN CIRCULAR NUMBER: 26029 SUBJECT: GRB 191017B: Swift/UVOT Upper Limits DATE: 19/10/18 14:37:28 GMT FROM: Sam LaPorte at PSU GRB 191017B: Swift/UVOT Upper Limits J. D. Gropp (PSU) and B. Sbarufatti (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 191017B 302 s after the BAT trigger (Sbarufatti et al., GCN Circ. 26021). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 26022) 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 302 452 147 >18.9 white 302 1010 334 >19.1 v 460 4806 255 >18.1 b 558 752 39 >18.3 u 533 727 39 >18.9 w1 509 702 39 >18.2 m2 484 852 39 >18.6 w2 609 4601 235 >20.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.11 in the direction of the burst (Schlegel et al. 1998).