TITLE:   GCN CIRCULAR
NUMBER:  33522
SUBJECT: GRB 230325A: Swift/UVOT Upper Limits
DATE:    23/03/26 15:23:20 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N Paul Kuin (UCL/MSSL) and M. J. Moss (GWU)report on behalf
of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of
GRB 230325A 102 s after the BAT trigger (Moss et al., GCN
Circ. 33516).   No optical afterglow consistent with the
XRT position (Goad et al. GCN Circ. 33518) 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           102          252          147         >20.1
u_FC               314          540          222         >19.2
white              102         4222          344         >20.8
v                 4434         4634          197         >18.9
b                 3818         4018          197         >20.0
u                  314         5106          277         >19.3
w1                4845         5045          197         >19.9
m2                4640         4839          197         >19.8
w2                4230         4429          197         >20.2
The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.046 in the
direction of the burst (Schlegel et al. 1998).