TITLE:   GCN CIRCULAR
NUMBER:  15433
SUBJECT: GRB 131031A: Swift/UVOT Upper Limits
DATE:    13/11/01 13:47:39 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

Paul Kuin (UCL/MSSL) and Eleonora Troja (GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began observations of the field of GRB 131031A
39.7ks after the ground-detected BAT trigger (Cummings, GCN
Circ. 15421). An otical afterglow candidate was reported
by Gorosabel et al. (GCN Circ. 15426) but no optical afterglow
consistent with the XRT position (Gompertz et al., GCN Circ. 15423)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the
initial exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white            40274        52042         1559         >21.1
v                40825        47155          762         >20.1
u                39724        51207         1559         >21.1

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).