TITLE: GCN CIRCULAR NUMBER: 18753 SUBJECT: GRB 151229A: Swift/UVOT observations DATE: 15/12/29 14:37:16 GMT FROM: Massimiliano de Pasquale at IASF-Palermo M. De Pasquale (UCL-MSSL) and D. Kocevski (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 151229A 90 s after the BAT trigger (Kocevski et al., GCN Circ. 18745). No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 18750) 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 90 240 147 >20.0 u_FC 302 552 246 >19.3 white 90 5493 378 >20.5 v 632 5904 413 >18.8 b 558 5288 236 >19.5 u 302 6513 653 >19.8 w1 681 6314 413 >19.7 m2 4474 6108 393 >19.9 w2 4064 5699 393 >20.0 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). -- Dr. Massimiliano De Pasquale Research associate - Swift UVOT scientist Mullard Space Science Laboratory, University College London