GCN Circular 40858

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
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 ).
No optical afterglow consistent with the enhanced XRT position
(Evans et al. GCN Circ. 40854
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 ) 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).