TITLE: GCN CIRCULAR NUMBER: 38365 SUBJECT: GRB 241127A: Swift/UVOT Detection DATE: 24/11/28 13:21:45 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk> A. A. Breeveld (UCL-MSSL) and C. Salvaggio (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 241127A 484 s after the BAT trigger (Salvaggio et al., GCN Circ. 38354). The optical counterpart seen in the UVOT at the position given in that circular, and also reported by Ortega-Cass et al., (GCN Circ. 38359) and MASTER (Buckley et al., GCN circular 38352 and Francile et al., GCN circular 38358) is detected in all the filters used for the initial UVOT exposures and is fading. Preliminary magnitudes 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 484 634 147 17.04 ± 0.03 white 16459 16862 393 19.81 +/1 0.09 b 15547 16453 885 20.3 ± 0.3 u 21787 22629 821 19.1 ± 0.1 v 10002 10870 847 19.7 ± 0.2 uvw1 20881 21780 886 19.5 ± 0.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.034 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/38365. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...