GCN Circular 38685

N. P. M. Kuin (UCL-MSSL) and V. D'Elia (SSDC & INAF-OAR)

report on behalf of the Swift/UVOT team:


The Swift/UVOT began settled observations of the field of
GRB 241228A  101 s after the BAT trigger (D'Elia et al.,
GCN Circ. 38681
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 ).  No optical afterglow consistent with
the XRT position in that circular was 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           101          251          147         >21.0
u_FC               314          564          246         >19.8
white              101         1538          392         >21.3
v                  644         1416           97         >19.1
b                  570         1514           97         >19.8
u                  314         1489          324         >20.0
w1                 694         1465           78         >19.2

The magnitudes in the table are not corrected for the
Galactic extinction due to the reddening of E(B-V) = 0.091
in the direction of the burst (Schlegel et al. 1998).