TITLE:   GCN CIRCULAR
NUMBER:  41162
SUBJECT: GRB 250725A: Swift/UVOT Upper Limits
DATE:    25/07/25 12:27:21 GMT
FROM:    s.shilling@lancaster.ac.uk

S. P. R. Shilling (Lancaster U.) and P. A. Evans (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250725A
880 s after the BAT trigger (Evans et al., GCN Circ. 41152).
No optical afterglow consistent with the enhanced XRT position
(Osborne et al., GCN Circ. 41153) 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           880         1029          147         >21.0
white              880         2562          322         >21.2
v                 1036         2439          175         >19.6
b                 1134         2537          175         >20.1
u                 1110         2340          156         >20.1
w1                1085         2488          175         >19.6
w2                1704         1898           39         >19.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.114 in the direction of the burst
(Schlegel et al. 1998).