TITLE:   GCN CIRCULAR
NUMBER:  15615
SUBJECT: GRB 131224A: Swift/UVOT Upper Limits
DATE:    13/12/26 17:44:22 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

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

The Swift/UVOT began settled observations of the field of GRB 131224A 
10748 s after the INTEGRAL trigger (Mereghetti et al., GCN Circ. 15607).
The field is very crowded and no optical afterglow consistent with the 
INTEGRAL position 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

u                10748        18662         3918         >21.1

The magnitudes in the table are not corrected for the strong Galactic 
extinction due to the reddening of E(B-V) = 0.96 in the direction of the 
burst (Schlegel et al. 1998).