TITLE: GCN CIRCULAR NUMBER: 19576 SUBJECT: GRB 160624A: Swift/UVOT Upper Limits DATE: 16/06/25 16:26:56 GMT FROM: Massimiliano de Pasquale at IASF-Palermo M. De Pasquale (UCL-MSSL) and A. D'Ai (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160624A 77 s after the BAT trigger (D'Ai et al., GCN Circ. 19560). No optical afterglow consistent with the XRT position (Beardmore et al. GCN Circ. 19566) is detected in the initial and summed UVOT exposures, nor at the position of the SDSS galaxy mentioned by Cucchiara et al. (GCN Circ. 19565). 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 77 227 147 >20.8 u_FC 289 527 234 >20.0 white 77 6288 541 >21.5 v 5060 6657 352 >19.5 b 4445 6082 393 >20.7 u 289 12622 1073 >20.7 w1 5471 11954 1082 >20.8 m2 5266 11048 1082 >20.7 w2 4855 6494 393 >20.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.07 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