TITLE:   GCN CIRCULAR
NUMBER:  31801
SUBJECT: GRB 220325A: Swift/UVOT Upper Limits
DATE:    22/03/28 16:02:38 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and M. Ferro (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 220325A
114 s after the BAT trigger (Ferro et al., GCN Circ. 31787).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 31790)
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           114          264          147         >20.8
u_FC               326          576          246         >20.1
white              114         5035          488         >21.0
v                  657         1234           78         >18.7
b                  582         4893          255         >20.1
u                  326         4688          481         >20.3
w1                 707          726           19         >17.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.915 in the direction of the burst
(Schlegel et al. 1998).