TITLE: GCN CIRCULAR NUMBER: 16472 SUBJECT: GRB 140628A: Swift/UVOT Detection DATE: 14/06/28 21:52:10 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and E. Sonbas (NASA/GSFC/Adiyaman Univ.) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 140628A 278 s after the BAT trigger (Sonbas et al., GCN Circ. 16467). A source consistent with the XRT position (D'Avanzo et al. GCN Circ. 16470) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 02:42:39.88 = 40.66617 (deg.) Dec (J2000) = -00:23:05.7 = -0.38491 (deg.) with an estimated uncertainty of 0.46 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 278 327 48 17.43 +/- 0.08 white 3593 4974 300 >21.0 v 3749 3949 197 19.08 +/- 0.28 b 4569 4769 197 >20.2 u 4364 4564 197 >19.5 w1 4159 4359 197 >19.8 m2 3954 4154 197 >21.2 w2 9366 10266 886 >21.1 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).