TITLE:   GCN CIRCULAR
NUMBER:  22202
SUBJECT: GRB 171205A: Continued Swift/UVOT Observations
DATE:    17/12/07 17:40:15 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU), P. J. Brown (Mitchell Institute, TAMU), 
S.W.K. Emery (UCL-MSSL) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT has continued observations of the optical transient in
GRB 171205A (D’Elia et al., GCN Circ. 22177).  We find that photometry
in the optical passbands is consistent with either steady flux or slight
decline, consistent with the report of Mao et al. (GCN Circ. 22195).  However,
all four UV passbands show a significant decay over the first day of
observations.  Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:

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


white       155       3850       183     18.05+-0.07
white      5524      28415      1081     17.85+-0.05
white    188009     193590       703     18.58+-0.08
v          5934      22497       903     18.09+-0.08
v         46094      57628       150     18.26+-0.24
v         74068     142426       350     18.20+-0.12
b          3608       3808       196     18.69+-0.10
b         26595      27502       885     18.53+-0.06
b         38171      61189       254     18.43+-0.08
b         67064     141691       379     18.69+-0.08
u           312        391        77     17.75+-0.18
u         16032      16558       513     17.54+-0.06
u         38114      61132       254     17.66+-0.08
u         67030     141669       379     18.32+-0.09
uvm2       9466      10366       885     16.67+-0.06
uvm2      46150      57780       435     18.37+-0.15
uvm2      74102     142498      1315     18.71+-0.11
uvw1      10373      16025      1066     16.95+-0.06
uvw1      38031      61074       383     17.93+-0.10
uvw1      66981     141647       568     18.51+-0.11
uvw2       5729      28438      1098     17.06+-0.07
uvw2      40218     141597      2322     18.68+-0.08
uvw2      73989     142404       877     18.82+-0.12

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998), nor from any contribution of the host galaxy.