TITLE:   GCN CIRCULAR
NUMBER:  14113
SUBJECT: GRB 121226A: Swift/UVOT Upper Limits
DATE:    12/12/27 21:17:57 GMT
FROM:    Alice Breeveld at MSSL-UCL  <aab@mssl.ucl.ac.uk>

A. A. Breeveld (MSSL-UCL) and H. A. Krimm (CRESST/GSFC/USRA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 121226A 
104 s after the BAT trigger (Krimm et al., GCN Circ. 14105). No optical 
afterglow consistent with the XRT position (Littlejohns et al. GCN Circ. 
14112) 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           104          254          147         >20.6
u_FC               317          566          246         >19.6
white              104        18160         1317         >21.6
v                  646        10716         1121         >20.4
b                  572        17397         1317         >21.3
u                  317        16485         1544         >20.9
w1                 696        12390         1163         >20.7
m2                 671        11621         1298         >21.0
w2                 622         6620          351         >20.2

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.055 in the direction of 
the burst (Schlegel et al. 1998).