TITLE: GCN CIRCULAR NUMBER: 16130 SUBJECT: GRB 140419A: Swift UVOT refined analysis DATE: 14/04/19 21:55:33 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and F. E. Marshall (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 140419A 97 s after the BAT trigger (Marshall et al. GCN Circ. 16118). Optical and IR photometry and positions were reported, as well as a redshift (Cenko, et al., GCN Circ. 16129; Hentunen et al., GCN Circ. 16126; Tanvir et al., GCN Circ. 16125; Kuin et al., GCN Circ. 16123; Butler et al., GCN Circ. 16121; Guver et al., GCN Circ. 16120; and Zheng et al., GCN Circ. 16119.) A source consistent with the XRT position is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 08:27:57.56 = 126.98982 (deg.) Dec (J2000) = +46:14:25.3 = 46.24037 (deg.) with an estimated uncertainty of 0.50 arc sec. (radius, 90% confidence). Due to the GRB lying on the edge of a large scattered light feature from the bright star nearby, photometry errors are large until a good background template can be made at late times. Preliminary detections and 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 97 246 147 16.2 +/- 0.2 v 638 658 19 16.1 +/- 0.2 b 564 756 39 18.4 +/- 0.2 u 309 2003 362 >21.0 w1 687 707 19 >18.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).