TITLE:   GCN CIRCULAR
NUMBER:  40619
SUBJECT: GRB 250603A: Swift/UVOT Upper Limits
DATE:    25/06/03 13:14:52 GMT
FROM:    Samantha Oates at University of Birmingham <samantha.oates@alumni.ucl.ac.uk>

S. R. Oates (Lancaster U.) and T. M. Parsotan (GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250603A
105 s after the BAT trigger (Parsotan et al., GCN Circ. 40613).
No optical afterglow consistent with the enhanced XRT position
(Beardmore et al., GCN Circ. 40616) 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           105          255          147         >20.4
u_FC               318          567          246         >19.7
white              105         1531          382         >21.0
v                  647         5129          190         >19.0
b                  573         1516           97         >19.6
u                  318         1491          324         >19.8
w1                 697         1467           78         >18.7
m2                 672         1442           97         >18.5
w2                 623         5029          294         >19.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.89 in the direction of the burst
(Schlegel et al. 1998).