TITLE: GCN CIRCULAR NUMBER: 21955 SUBJECT: GRB 171001A: Swift/UVOT Detection DATE: 17/10/02 09:52:10 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and A. Y. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 171001A 198 s after the BAT trigger (Lien et al., GCN Circ. 21946). The source was found in the IR J band by Itoh et al. (GCN. Circ. # 21954). We find a source consistent with the XRT position (Evans et al. GCN Circ. 21952) in the initial UVOT exposures. Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 198 1359 373 21.23 +/- 0.30 v 686 1409 58 >18.2 b 612 1503 93 >19.8 u 356 780 265 >20.3 w1 736 1458 58 >20.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).