TITLE: GCN CIRCULAR NUMBER: 41491 SUBJECT: EP250821a: Swift/UVOT further observations. DATE: 25/08/22 09:44:34 GMT FROM: Samantha Oates at University of Birmingham <samantha.oates@alumni.ucl.ac.uk> S. R. Oates (Lancaster U.) and S. Dichiara (PSU) report on behalf of the Swift-XRT and Swift-UVOT team: Swift/UVOT has performed further follow-up observations of the Einstein Probe/WXT-detected source EP250821a (Hu et al., GCN 41459). The UVOT optical counterpart reported in (Dichiara et al., GCN 41469) has faded, consistent with the behaviour reported by Li et al. (GCN 41470) and Yao et al. (GCN 41485). The refined UVOT position is RA (J2000) 19:19:32.56 Dec (J2000) -43:22:52.3 with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence). We note that this position supersedes that reported in Dichiara et al. (GCN 41469), which is incorrect. We apologise for any confusion. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag/3sigUL v 61584 72904 799 >19.9 u 5186 11029 1897 18.88+\-0.08 (reported in GCN 41469) u 68377 68575 195 >19.8 uvw1 67966 68372 399 >20.0 uvm2 67555 67961 399 >19.8 uvw2 61180 72857 1168 >20.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.07 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/41491. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...