TITLE: GCN CIRCULAR NUMBER: 44467 SUBJECT: GRB 260504B: EP-FXT upper limit DATE: 26/05/05 04:30:12 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> H. Zhou (PMO, CAS), Y.Q. Zhao (PRIC, USTC), T.Y. Liu, Y. Liu (NAOC, CAS) on behalf of the Einstein Probe (EP) team: The Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission observed GRB 260504B (Saccardi, GCN 44454) autonomously at 2026-05-04 11:46:16 (UTC, ~ 2.25 hours after the burst). The exposure time of this observation is 1472s. On-ground analysis of the FXT data did not found any significant source within the error circle (90% C.L. radius of 167 arcsec) of GRB 260504B. The 5-sigma upper limit of EP-FXT observation is 4.8 x 10^-13 erg/s/cm^2 in the 0.5-10 keV band. 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/44467. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...