GCN Circular 32063

S. R. Oates (U.Birmingham) and J. D. Gropp (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 220518A
129 s after the BAT trigger (Gropp et al., GCN Circ. 32060
Not found
 
 
).
A source consistent with the enhanced XRT position
(Beardmore et al. GCN Circ. 32062
Not found
 
 
)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
   RA  (J2000) =  03:41:22.29 =  55.34289 (deg.)
   Dec (J2000) = -47:35:00.3  = -47.58342 (deg.)
with an estimated uncertainty of 0.55 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 (FC)        129          279         147         20.00 +/- 0.25
white             621         1717         334         20.49 +/- 0.23
v                 671         1767         136         >19.0
b                 597         1861         131         >20.1
u (FC)            341          591         246         >19.7
u                 341         1841         324         >19.9
w1               1103         1296          39         >18.4


The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.008 in the direction of the burst
(Schlegel et al. 1998).