TITLE:   GCN CIRCULAR
NUMBER:  15496
SUBJECT: GRB 131117A: Swift/UVOT Detection
DATE:    13/11/17 14:57:25 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and M. J. Page (UCL-MSSL) report on behalf of 
the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 131117A 
70s after the BAT trigger (Page et al., GCN Circ. 15490).
A fading source consistent with the afterglow position found by Trotter 
et al. (GCN Circ. 15491) is found in the white filter only. This is 
consistent with the redshift of z=4.042 given by Hartoog et al. (GCN 
Circ. 15494).

The preliminary UVOT position is:
     RA  (J2000) =  22:09:19.36 = 332.33067 (deg.)
     Dec (J2000) = -31:45:44.3  = -31.76231 (deg.)
with an estimated uncertainty of 0.64 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               70          219          147         20.13 ± 0.17
v                  611         5157          216        >20.0
b                  537         4542          216        >20.6
u                  282         4336          442        >20.7
w1                 660         5567          216        >20.4
m2                 636         5362          216        >20.0
w2                 587         4952          216        >20.5

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).