GCN Circular 23498

M. H. Siegel (PSU) and J. K. Cannizzo (NASA/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 181202A
86 s after the BAT trigger (Cannizzo et al., GCN Circ. 23482
Not found
 
 
).
A source consistent with the XRT position
(Evans et al. GCN Circ. 23483
Not found
 
 
)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
  RA  (J2000) =  18:42:56.38 = 280.73491 (deg.)
  Dec (J2000) = +27:57:35.0  =  27.95971 (deg.)
with an estimated uncertainty of 0.47 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

v                  623         1540          117        >18.7
b                  342          591          246         19.57 +/- 0.18
u (fc)              86          336          246         17.67 +/- 0.07
w1                 672         1441           97        >19.6
m2                 647         1560          112        >22.2
w2                 598         1516          117        >20.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.14 in the direction of the burst
(Schlegel et al. 1998).