TITLE:   GCN CIRCULAR
NUMBER:  19815
SUBJECT: GRB 160816A: Swift/UVOT Detection
DATE:    16/08/17 19:29:32 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

Paul Kuin (UCL/MSSL), D. Malesani (DARK/NBI and DTU Space), Frank
Marshall (GSFC) and Lea Hagen (PSU) report on behalf of the Swift/UVOT
team:

The Swift/UVOT began settled observations of the field of the Fermi/LAT-
detected GRB 160816A 25222 s after the LAT trigger (Racusin et al. GCN
Circ. 19802). A source consistent with the XRT position (Kennea et al.
GCN Circ. 19806) and the LCOGT Faulkes Telescope North position (Guidorzi
et al., GCN Circ. 19808) is detected in the initial UVOT exposures at the
same position as reported by RATIR (Troja et al, GCN. Circ. 19809).

Preliminary detections and 3-sigma upper limit 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            27601        43846          879         21.48 +/- 0.22
v                27661        27703           41        >17.9
u                25222        37523         2287         21.37 +/- 0.31

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.25 in the direction of the burst
(Schlegel et al. 1998).