GCN Circular 20074

A. A. Breeveld (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 161017A
68 s after the BAT trigger (Troja et al., GCN Circ. 20064
Not found
 
 
, Yurkov et 
al., GCN Circ. 20063
Not found
 
 
).
The UVOT source described in Troja et al., GCN Circ. 20064
Not found
 
 
, is at a 
position consistent with the enhanced XRT position (Beardmore et al., 
GCN Circ. 20067
Not found
 
 
) and is found to be fading.

The preliminary UVOT position is:
     RA  (J2000) =  09:31:04.60 = 142.76915 (deg.)
     Dec (J2000) = +43:07:36.3  =  43.12676 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).

Preliminary detections 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               68          217          147         14.08 �� 0.02
v                  609          629           20         15.14 �� 0.09
b                  535          555           20         15.60 �� 0.06
u                  280          529          246         14.56 �� 0.02
uvw1               658          661          2.7         15.5  �� 0.3

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.02 in the direction of the 
burst (Schlegel et al. 1998).