GCN Circular 21955

N. P. M. Kuin (UCL-MSSL) and A. Y. Lien (GSFC/UMBC) report on behalf of
the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 171001A
198 s after the BAT trigger (Lien et al., GCN Circ. 21946
Not found
 
 
). The source
was found in the IR J band by Itoh et al. (GCN. Circ. # 21954). We find
a source consistent with the XRT position (Evans et al. GCN Circ. 21952
Not found
 
 
) 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              198         1359          373         21.23 +/- 0.30
v                  686         1409           58        >18.2
b                  612         1503           93        >19.8
u                  356          780          265        >20.3
w1                 736         1458           58        >20.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).