TITLE:   GCN CIRCULAR
NUMBER:  20159
SUBJECT: GRB 161108A: Swift/UVOT Upper Limits
DATE:    16/11/09 18:46:33 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) and A. P. Beardmore (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 161108A
90 s after the BAT trigger (Beardmore et al., GCN Circ. 20131).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 20147) or the NOT position (Malesani et al.,
GCN Cir., 20146) 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 initial exposures are:

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

white (fc)         90          239          147         >20.08
white              90         5617          344         >20.62
v                 578         6029          235         >18.61
b                5212         5412          196         >19.76
u                 248          498          245         >19.24
u                 248        10794          652         >19.88
uvw1              628         6439          412         >19.66
uvm2              603         6234          412         >19.89
uvw2              554         5823          235         >19.59

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).