GCN Circular 22827

A. A. Breeveld (UCL-MSSL), P. A. Evans (U. Leicester) and M. De Pasquale 
(U. Instanbul) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180620B 92 
s after the BAT trigger (Evans et al., GCN Circ. 22807
Not found
 
 
).
A source consistent with the enhanced XRT position (Beardmore et al., 
GCN Circ. 22814
Not found
 
 
) and the Grond position (Schweyer and Schady, GCN Circ. 
22819
Not found
 
 
), and also detected by Izzo et al. (GCN Circ. 22823
Not found
 
 
) is detected 
in the initial UVOT exposures in all filters except uvw2. The 
non-detection in the uvw2 filter is consistent with the redshift of 1.12 
(Izzo et al. GCN Circ. 22823
Not found
 
 
).

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               92          242          147         18.06 �� 0.08
v                  634          826           39         17.41 �� 0.22
b                  559          579           20         17.56 �� 0.18
u                  304          554          246         17.40 �� 0.09
uvw1              9950        18219         1394         20.17 �� 0.2
uvm2              6563        16382          804         20.6 �� 0.3
uvw2              4256         4443          183         > 19.7

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.01 in the direction of the 
burst (Schlegel et al. 1998).