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).