TITLE: GCN CIRCULAR NUMBER: 17242 SUBJECT: GRB 141225A: Swift/UVOT refined analysis DATE: 14/12/26 18:37:57 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 141225A 428 s after the BAT trigger (D'Avanzo et al., GCN Circ. 17229). The optical afterglow has been reported (Gorosabel et al, GCN Circ. 17230; Guidorzi et al., GCN Circ. 17231; Malesani et al., GCN Circ. 17232; Kuin & D'Avanzo, GCN.Circ. 17233; Xu et al., GCN Circ. 17236; Buckley et al., 17237; Sonbas et al., GCB Circ. 17240) with a redshift of z=0.915 (Gorosabel et al., GCN Circ. 17234). 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 428 578 147 18.81 +/- 0.06 white 858 1008 147 19.76 +/- 0.10 v 735 1406 78 >19.2 b 660 1495 86 >19.5 u 636 1481 97 19.19 +/- 0.19 w1 611 1456 97 >19.0 m2 760 780 19 >18.6 w2 6480 6680 197 >19.7 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).