GCN Circular 16791

NPM Kuin (UCL/MSSL), and H. A. Krimm (CRESST/GSFC/USRA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 140907A
(Krimm et al., GCN Circ. No. 16788) 107 seconds after the trigger.

There is a candidate afterglow in the rapidly available 2.7'x2.7'
sub-image at
RA(J2000)  =  03:12:34.98 = 48.14575
DEC(J2000) = +46:36:17.5  = 46.60486
with a 90%-confidence error radius of about 0.75 arc sec, consistent
with the optical position from Xu et al. (GCN.Circ.No <http://gcn.circ.no/>.
16789).

Preliminary magnitudes observed in the initial images using the UVOT
photomatric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373)
are:

Filter  T_start(s) T_stop(s) Exp(s)   Mag
white   107        257       150      16.66 +/- 0.04
u       321        534       213      16.61 +/- 0.06

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.29 in the direction of the burst
(Schlegel et al. 1998).