GCN Circular 32470

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

The Swift/UVOT began settled observations of the field of GRB 220813A
100 s after the BAT trigger (Bernardini et al., GCN Circ. 32465
Not found
 
 
).
A source consistent with the XRT position (Osborne et al.,
GCN Circ. 32466
Not found
 
 
) is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  05:26:07.60 =  81.53166 (deg.)
    Dec (J2000) = -33:00:59.0  = -33.01638 (deg.)
with an estimated uncertainty of 0.52 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT photometric
system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures
are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              100          250          147         19.67 +/- 0.11
v                  589         1581          117        >18.3
b                  515         1506           97        >19.6
u                  258         1652          360        >20.6
w1                 638         1630          117        >19.6
m2                 613         1605          117        >20.1
w2                 564         1556          117        >20.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.022 in the direction of the burst
(Schlegel et al. 1998).