TITLE:   GCN CIRCULAR
NUMBER:  23581
SUBJECT: GRB 181228A: Swift/UVOT Upper Limits
DATE:    18/12/28 16:53:43 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

GRB 181228A: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and M. J. Moss (George Washington University)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 181228A
93 s after the BAT trigger (Moss et al., GCN Circ. 23570).
No optical afterglow consistent with the XRT position
(Moss et al. GCN Circ. 23570)
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            93          243          147         >20.4
u_FC               305          555          246         >20.6
white               93         1354          373         >21.0
v                  634         1404           97         >19.1
b                  561         1330           78         >20.5
u                  305         1305          304         >20.5
w1                 684         1280           39         >18.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.51 in the direction of the burst
(Schlegel et al. 1998).