GCN Circular 16828

M. H. Siegel (PSU) and J. L. Racusin (NASA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 140916A
160 s after the BAT trigger (Racusin et al., GCN Circ. 16819
Not found
 
 
).
No optical afterglow consistent with the XRT position
(Evans GCN Circ. 16820
Not found
 
 
)
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           160          310          147         >21.5
u_FC               318          568          246         >20.7
white              160         6731          608         >22.3
v                  648        12894         1415         >21.2
b                  574        19208          857         >20.8
u                  318        24969         2113         >21.4
w1                 697        30730         2826         >21.9
m2                 844        30169         2742         >21.7
w2                 796        29263         2203         >22.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).