TITLE: GCN CIRCULAR NUMBER: 44642 SUBJECT: GRB 260515A: EP-FXT follow-up observation DATE: 26/05/16 09:39:53 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> Z.M. Wang (BNU), X.X. Sun(NAO, CAS), Y.H.Cheng (SWIFAR, YNU), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed an automatic follow-up observation of GRB 260515A detected by SVOM/ECLAIRs (SVOM/sb26051504, Brunet et al., GCN 44622). The follow-up obervation started at 2026-05-15T20:51:27 UTC, approximately 1.7 hours after the SVOM trigger, with a total exposure time of 5.9 ks. On-ground analysis of the FXT data found an uncatalogued fading source within the ECLAIRs error circle at R.A., Dec. = 227.6846, 24.5566 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). This position is consistent with the optical counterpart (He et al., GCN 44623; Saccardi et al., GCN 44624; Sosnovskij et al., GCN 44625; He et al., GCN 44626; Wu et al., GCN 44628; Dennefeld et al., GCN 44633; Li et al., GCN 44634). The average FXT 0.3-10 keV spectrum can be fitted with an absorbed power-law model, with the hydrogen column density fixed at the Galactic value of 3.47×10^20 cm^-2 and a photon index of 1.71(-0.09/+0.09). The derived average unabsorbed flux in the 0.3-10 keV band is 7.13(-0.19/+0.21) x 10^(-12) erg/s/cm^2. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/44642. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...