TITLE: GCN CIRCULAR NUMBER: 42786 SUBJECT: GRB 251118A: Swift/UVOT Detection DATE: 25/11/20 22:23:37 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18@psu.edu> M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251118A 31.3 ks after the Fermi trigger (GCN Circ. 42743). A fading source consistent with the XRT position (Osbourne et al., GCN Circ. 42782) is detected in the UVOT exposures. The preliminary UVOT position is: RA (J2000) = 10:14:01.01 = 160.00422 (deg.) Dec (J2000) = -34:31:21.1 = -34.52254 (deg.) with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence). 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 31521 52651 885 18.79+/-0.05 white 108251 159027 1113 20.11+/-0.10 v 31678 42929 845 18.60+/-0.19 v 108564 147691 662 >19.73 u 31363 52627 2489 18.41+/-0.05 u 107942 158555 1113 19.61+/-0.15 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.057 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42786. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...