TITLE: GCN CIRCULAR NUMBER: 44578 SUBJECT: GRB 260511B: EP-FXT follow-up observation DATE: 26/05/12 12:55:37 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> S.-Y. Fu (HUST), X. Tian (GXU), H.-N. Yang, Z.-X. Ling (NAOC, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of GRB 260511B detected by Fermi/GBM (the Fermi GBM team, GCN 44542) and SVOM/ECLAIRs (SVOM/sb26051102, Godet et al., GCN 44543). The follow-up obervation started at 2026-05-11T11:41:41 UTC, approximately 40.7 minutes 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 at R.A., Dec. = 192.574, 4.0549 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic) near the ECLAIRs error circle. This position is consistent with the optical counterpart reported by SVOM/C-GFT (Wu et al., GCN 44547) and MITSuME (Sasada et al. GCN 44549). 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, intrinsic hydrogen column density of 3.8 (+-0.10) ×10^21 cm^-2, and a photon index of 2.10 +- 0.04. The derived average unabsorbed flux in the 0.3-10 keV band is 2.07 (+-0.05)×10^-11 erg s^-1 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/44578. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...