TITLE: GCN CIRCULAR NUMBER: 17726 SUBJECT: GRB150418A: Swift/UVOT did not detect a new source DATE: 15/04/21 23:05:38 GMT FROM: Paul Kuin at MSSL N.P.M. Kuin (UCL/MSSL) reports on behalf of the Swift UVOT team: Swift UVOT observations were made concurrently with the XRT observations reported by Sbarufatti et al. (GCN Circ. 17722 and 17725) of GRB 150418A which was discovered by MAXI (Serino et al., GCN Circ. No. 17719). At the location of the possible X-ray source detections named source 1 and source 2 no new source was detected in the u-band, with the following limits: Source 1: u > 22.9 at 72.2 ks since the MAXI trigger at 2015-04-18T00:52:08UT for an exposure time of 3.9ks Source 2: u > 21.17 at t = 19ks since the MAXI trigger, for an exposure time of 322s. However, we note that source 1 is at a distance of 4.6 arcsec of a known nearby source in GSC2.3 (designated S5FU004949). That source was detected with a magnitude u=20.38 +/- 0.15. No correction was made for the galactic reddening of E(B-V) = 0.043 and 0.373 respectively (Schlafly & Finkbeiner 2011 (ApJ 737, 103) ) at the locations of the sources 1 and 2.