GCN Circular 20455

M. H. Siegel (PSU) and P. A. Evans (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 170113A
68 s after the BAT trigger (Evans et al., GCN Circ. 20446
Not found
 
 
).
A fading source consistent with the XRT position
(Goad et al. GCN Circ. 20450
Not found
 
 
)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
   RA  (J2000) =  04:06:55.86 =  61.73276 (deg.)
   Dec (J2000) = -71:56:34.9  = -71.94302 (deg.)
with an estimated uncertainty of 0.44 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

white (fc)          68          217          147         18.27+-0.06
white              560         1009          186         19.56+-0.11
white             1163         1875           97         19.65+-0.17
white             6392         6592          196         20.64+-0.26
v                  609         1751          136         19.09+-0.36
v                 5367         7002          393         >19.49
b                  535         1850          136         19.33+-0.19
b                 6188         6388          196         >20.39
u (fc)             280          530          245         18.76+-0.13
u                  683         1825          116         19.33+-0.27
u                 5983         7615          390         >20.44
uvw1               659         1801          136         >19.38
uvm2               634         1776          136         >19.12
uvw2               585         1727          136         >19.42

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.11 in the direction of the burst
(Schlegel et al. 1998).