TITLE: GCN CIRCULAR NUMBER: 18531 SUBJECT: GRB 151029A: Swift/UVOT Detection DATE: 15/10/29 19:51:56 GMT FROM: Samantha Oates at MSSL S. R. Oates (IAA-CSIC/UCL-MSSL) and T. N. Ukwatta (LANL) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 151029A 92 s after the BAT trigger (Ukwatta et al., GCN Circ. 18522). A source consistent with the XRT position (Beardmore et al., GCN Circ. 18526) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 02:34:06.72 = 38.52799 (deg.) Dec (J2000) = -35:23:08.6 = -35.38573 (deg.) with an estimated uncertainty of 0.42 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 92 242 147 16.98 +/- 0.03 v 634 653 19 17.66 +/- 0.32 b 560 752 39 19.24 +/- 0.33 u 304 554 246 17.35 +/- 0.06 w1 683 703 19 >17.98 m2 658 850 39 >18.17 w2 609 802 39 >18.64 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).