TITLE:   GCN CIRCULAR
NUMBER:  21329
SUBJECT: GRB 170711A: Swift/UVOT Upper Limits
DATE:    17/07/12 16:20:43 GMT
FROM:    Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 170711A
124 s after the BAT trigger (D'Elia et al., GCN Circ. 21321).
No optical afterglow consistent with the enhanced XRT position
(Beardmore et al. GCN Circ. 21323) 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 initial exposures are:

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

u_FC               124          374          246         >19.8
v                  430         1553          136         >18.9
b                  379         1503          156         >19.4
w1                 480         1454           97         >19.6
m2                 604         1429           58         >18.6
w2                 704         1380           78         >19.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.31 in the direction of the burst
(Schlegel et al. 1998).