TITLE:   GCN CIRCULAR
NUMBER:  18293
SUBJECT: GRB 150911A: Swift/UVOT Upper Limits
DATE:    15/09/12 15:18:00 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

GRB 150911A: Swift/UVOT Upper Limits

F. E. Marshall (NASA/GSFC) and R. L. C. Starling (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150911A
82 s after the BAT trigger (Starling et al., GCN Circ. 18280).
No optical afterglow consistent with the enhanced XRT position
(Goad et al. GCN Circ. 18283) 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            82          232          147         >20.6
u_FC               294          544          246         >20.2
white               82         1702          400         >21.2
v                  623         1590          117         >18.9
b                  549         1689          117         >19.4
u                  294         1665          343         >20.4
w1                 673         1640          117         >19.1
w2                 772         1565           97         >19.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.32 in the direction of the burst
(Schlegel et al. 1998).