GCN Circular 41521

Paul Kuin (UCL/MSSL) and M. H. Siegel (PSU) report on behalf of the
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250823A
126 s after the BAT trigger (Siegel et al., GCN Circ. 41511
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 ). A source
consistent with the XRT position is detected in the initial UVOT exposures.

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              126         1020          334         20.42 +/- 0.17
v                  668         1244           78         18.43 +/- 0.28
b                  594         1169           58         19.25 +/- 0.28
u                  338         1317          304        >19.5
w1                 718         1293           58        >19.1
m2                 692         1268           58        >18.8
w2                 644         1391           97        >19.3

The magnitudes in the table are not corrected for the Galactic extinction due
to the reddening of E(B-V) = 0.111 in the direction of the burst (Schlegel
et al. 1998).