TITLE:   GCN CIRCULAR
NUMBER:  19963
SUBJECT: GRB 160927A: Swift/UVOT Upper Limits
DATE:    16/09/28 16:13:58 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

Paul Kuin(MSSL-UCL) and S. L. Gibson (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160927A
85 s after the BAT trigger (Gibson et al., GCN Circ. 19952).
No optical afterglow consistent with the optical position
(D'Avanzo et al. GCN Circ. 19956)
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            85          235          147         >21.0
u_FC               297          547          246         >20.4
white               85        13184         1426         >21.8
v                  627         6999          510         >19.9
b                  553        12500         1179         >21.5
u                  297        11587         1433         >21.1
w1                 850         7411          491         >20.2
m2                 826         7204          294         >20.5
w2                 602         6794          510         >21.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.08 in the direction of the burst
(Schlegel et al. 1998).