GCN Circular 19815

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
Not found
 
 
). A source consistent with the XRT position (Kennea et al.
GCN Circ. 19806
Not found
 
 
) and the LCOGT Faulkes Telescope North position (Guidorzi
et al., GCN Circ. 19808
Not found
 
 
) 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).