TITLE:   GCN CIRCULAR
NUMBER:  39861
SUBJECT: GRB 250322A: Swift/UVOT Upper Limits
DATE:    25/03/24 12:52:39 GMT
FROM:    Sam Shilling at Lancaster University <shilling.sam@gmail.com>

S. P. R. Shilling (Lancaster U.) and R. Gupta (NASA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250322A
77 s after the BAT trigger (Gupta et al., GCN Circ. 39835).
No optical afterglow consistent with the enhanced XRT position
(Goad et al., GCN Circ. 39841) 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            77          226          147         >20.5
u_FC               291          541          246         >19.8
white               77         1711          411         >20.9
v                  620         1760          136         >18.9
b                  546         1686          117         >19.7
u                  291         1661          343         >20.0
w1                 669         1807          134         >19.2
m2                 644         1785          136         >19.0
w2                 596         1736          136         >19.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.153 in the direction of the burst
(Schlegel et al. 1998).