TITLE: GCN CIRCULAR NUMBER: 40858 SUBJECT: GRB 250628A: Swift/UVOT Upper Limits DATE: 25/06/28 12:44:42 GMT FROM: Paul Kuin at MSSL npkuin@gmail.com
Paul Kuin (MSSL/UCL) and M Ferro (INAF-OAB) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250628A 130 s after the BAT trigger (Ferro et al., GCN Circ. 40853). No optical afterglow consistent with the enhanced XRT position (Evans et al. GCN Circ. 40854) 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 130 280 147 >20.8 u_FC 342 591 246 >19.3 white 130 641 167 >20.8 v 671 691 19 >17.8 b 597 617 19 >18.5 u 342 591 246 >19.3 w1 720 740 19 >18.2
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.023 in the direction of the burst (Schlegel et al. 1998).
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