TITLE:   GCN CIRCULAR
NUMBER:  16717
SUBJECT: GRB 140818B: Swift/UVOT Upper Limits
DATE:    14/08/19 13:10:44 GMT
FROM:    Lea Hagen at PSU  <lea.zernow.hagen@gmail.com>

L. M. Z. Hagen (PSU) and A. Vargas (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 140818B
114 s after the BAT trigger (Vargas et al., GCN Circ. 16709).  No optical
afterglow consistent with the XRT position (Beardmore et al. GCN Circ.
16712), the OSN candidate (Aceituno et al. GCN Circ 16711), or the GROND
candidate (Knust et al. GCN Circ 16713) 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 early
exposures are:

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

white              113         5136          530         >21.32
v                  654         5546          254         >19.28
b                  581         4931          235         >20.11
u                  325         6007          506         >20.17
uvw1               704         5956          416         >19.92
uvm2              5551         5751          196         >19.53
uvw2               803         5341          235         >19.97

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.70 in the direction of the burst
(Schlegel et al. 1998).