GCN Circular 18753

M. De Pasquale (UCL-MSSL) and D. Kocevski (NASA/GSFC/ORAU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 151229A
90 s after the BAT trigger (Kocevski et al., GCN Circ. 18745
Not found
 
 
).
No optical afterglow consistent with the XRT position (Osborne et al.
GCN Circ. 18750
Not found
 
 
) 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            90          240          147         >20.0
u_FC               302          552          246         >19.3
white               90         5493          378         >20.5
v                  632         5904          413         >18.8
b                  558         5288          236         >19.5
u                  302         6513          653         >19.8
w1                 681         6314          413         >19.7
m2                4474         6108          393         >19.9
w2                4064         5699          393         >20.0

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).

-- 

Dr. Massimiliano De Pasquale
Research associate - Swift UVOT scientist
Mullard Space Science Laboratory, University College London