GCN Circular 45988

N.P.M. Kuin, A.A. Breeveld, M.J. Page (MSSL/UCL) and M. H. Siegel (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 261017A
90 s after the BAT trigger (Siegel et al., GCN Circ. 45974
Loading...
 
 ).
A source consistent with the XRT position (Beardmore et al.,GCN Circ. 45977)
is detected in the initial UVOT exposures.

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               90         1377          373         20.41 +/- 0.24
v                  631         1427           97        >18.6
b                  557         5666          198        >19.2
u                  302         5538          501        >19.2
w1                 680         1304           78        >18.5

The source varies between exposures, is sometimes absent, and
appears double in two images. It might not be a point source.

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.023 in the direction of the burst
(Schlegel et al. 1998).