TITLE: GCN CIRCULAR NUMBER: 45139 SUBJECT: EP260711a: Einstein Probe detection of an X-ray transient DATE: 26/07/12 03:24:47 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> Y.Wu (NJU), G. Y. Zhao (SYSU), H. W. Peng (THU), and H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient, designated EP260711a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission . The transient was identified in the telemetry data. The transient started at 2026-07-11T09:19:04 (UTC) and lasted for about 75s, with a peak flux of ~ 1.52 x 10^(-9) erg cm^-2 s^-1 in 0.5-4 keV. The position of the transient is R.A. = 213.2511 deg, Dec. = -58.8603 deg (J2000), with an uncertainty radius of 2.85 arcmin in radius (90% confidence level, including both statistical and systematic uncertainties). There are no known X-ray sources in the WXT error circle. The average WXT 0.5-4 keV spectrum can be fitted by an absorbed power-law model with a fixed Galactic hydrogen column density of 1.30 (-0.58/+2.27) ×10^22 cm^-2 and a photon index of 2.49 (-1.29/+1.59). The derived average unabsorbed 0.5-4 keV flux is 2.31 (-1.18/+7.48) x 10^(-10) erg cm^-2 s^-1. The uncertainties are at the 90% confidence level for the above parameters. Follow-up observations by EP-FXT will be arranged. Launched on 2024 January 9, Einstein Probe is a space-based X-ray observatory designed to monitor the dynamic X-ray sky and perform rapid follow-up observations of newly discovered transients (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/45139. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...