[vsnet-grb-info 14162] GRB 131108A: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15476
SUBJECT: GRB 131108A: Swift/UVOT Detection 
DATE:    13/11/09 16:54:16 GMT
FROM:    Margaret Chester at PSU  <chester at astro.psu.edu>

M.M. Chester and M. C. Stroh (PSU) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of the Fermi/LAT-detected 
GRB 131108A 25920 s after the LAT trigger (Racusin et al., GCN Circ. 15464).
A source consistent with the XRT position (Stroh and Kennea GCN Circ. 15474)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
   RA  (J2000) =  10:26:00.45 = 156.50187 (deg.)
   Dec (J2000) = +09:39:44.1  =   9.66225 (deg.)
with an estimated uncertainty of 0.58 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            27746        28046          295         19.70 +/- 0.10
b                26833        27133          295         19.67 +/- 0.16
u                25920        26220          295         19.10 +/- 0.14
w1               31699        32599          886         20.96 +/- 0.33
m2               37465        37914          442        >20.6
w2               45446        49794         1069        >21.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.028 in the direction of the burst
(Schlegel et al. 1998).