TITLE: GCN CIRCULAR NUMBER: 16932 SUBJECT: GRB 141020A: Swift/UVOT Detection DATE: 14/10/20 15:59:40 GMT FROM: Paul Kuin at MSSL N.P. M. Kuin (UCL-MSSL) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 141020A 92 s after the BAT trigger (Cenko et al., GCN Circ. 16928). A source consistent with the XRT position (Osborne et al. GCN Circ. 16931) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 14:59:59.15 = 224.99646 (deg.) Dec (J2000) = +55:18:46.7 = 55.31297 (deg.) with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence). 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 92 241 147 18.02 +/- 0.04 v 634 1409 58 18.40 +/- 0.23 b 559 753 39 18.66 +/- 0.18 u 304 554 246 18.48 +/- 0.09 w1 683 6660 471 >20.9 m2 1238 6455 413 >21.1 w2 784 11546 1196 >21.8 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).