TITLE: GCN CIRCULAR NUMBER: 42863 SUBJECT: GRB 251126A: Swift/UVOT Detection DATE: 25/11/27 14:51:12 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk> A.A. Breeveld (UCL-MSSL) and R. Caputo (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251126A 86s after the BAT trigger (Caputo et al., GCN Circ. 42843). The fading optical afterglow (Swain et al., GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Angulo et al., GCN 42855; Pulido-Torres et al., GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858; Seki et al., GCN 42859 and Volnova et al., GCN 42861) is clearly detected in the initial UVOT exposures. The non detection in the U and UV filters is consistent with the redshift of z=3.5 found by Angulo et al., (GCN Circ. 42855). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposures and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 86 236 147 20.0 ± 0.1 white 579 772 39 20.3 ± 0.3 white 880 1377 186 20.5 ± 0.2 u_FC 299 548 246 >20.4 v 629 1080 58 18.7 ± 0.3 b 1159 1352 39 19.4 ± 0.3 uvw1 853 1467 35 >18.32 uvm2 653 847 39 >18.00 uvw2 778 1402 58 >18.70 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.063 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42863. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...