TITLE:   GCN CIRCULAR
NUMBER:  20282
SUBJECT: GRB 161217A: Swift/UVOT Upper Limits
DATE:    16/12/17 17:26:54 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 161217A
163 s after the BAT trigger (D'Elia et al., GCN Circ. 20276).
No optical afterglow consistent with the enhanced XRT position
(Osborne et al., GCN Circ. 20278)
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) exposures and subsequent exposures are:

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

white_FC           163          308          142         >21.0
u_FC               314          564          246         >21.0
white              163         1713          406         >21.2
v                  644         1589          117         >18.8
b                  576         1689          111         >19.8
u                  314         1664          343         >20.4
w1                 693         1639           97         >20.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).