TITLE:   GCN CIRCULAR
NUMBER:  14169
SUBJECT: GRB 130131B: Swift/UVOT Upper Limits
DATE:    13/02/01 03:17:28 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 130131B
114 s after the BAT trigger (Siegel et al., GCN Circ. 14159).
No optical afterglow consistent with the XRT 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 first
finding chart (FC) exposure and subsequent exposures are:

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

white_FC           114          264          147         >20.9
u_FC               327          577          246         >20.2
white              114         6416          449         >22.0
v                 3871         5506          393         >19.8
b                  583         6325          413         >20.5
u                  327         6120          639         >21.0
w1                4281         5915          393         >20.4
m2                4076         5710          393         >20.6
w2                5101         5301          197         >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).