TITLE:   GCN CIRCULAR
NUMBER:  19860
SUBJECT: GRB 160824A: Swift/UVOT Possible Afterglow Detection
DATE:    16/08/25 14:25:28 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and P. A. Evans (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160824A
101 s after the BAT trigger (Evans et al., GCN Circ. 19855).
UVOT marginally detects a source consistent with the enhanced XRT position
(Goad et al. GCN Circ. 19857)
in the initial UVOT exposure with the white filter.

The preliminary analysis produces the following marginal detection 
and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373):

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

white              101          787          186         20.16 +/- 0.27
v                  645          837           39        >17.9
b                  571          763           39        >18.7
u                  313          738          265        >19.7
w1                 694          714           19        >18.5
m2                 669          861           39        >19.2
w2                 620          813           39        >18.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.69 in the direction of the burst
(Schlegel et al. 1998).