TITLE: GCN CIRCULAR NUMBER: 45513 SUBJECT: EP260903a: EP-WXT detection of a fast X-ray transient DATE: 26/09/04 08:19:20 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> Z.-M. Wang (BNU), R.-Z. Li (YNAO, CAS), R. Shi (PMO, CAS), H. Sun (NAO,CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient, designated EP260903a (notice ID: 13600875138), by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient was identified in the telemetry data. The WXT light curve of the transient started at about 2026-09-03T11:17:59 (UTC) and lasted for approximately 200 s, exhibiting a double-peaked structure. The position of the transient is R.A. = 292.004 deg, Dec. = -21.494 (J2000), with an uncertainty radius of 2.6 arcmin in radius (90% confidence level, including both statistical and systematic uncertainties). 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 8.0×10^20 cm^-2 and a photon index of 1.67 (-0.54/+0.60). The derived average unabsorbed 0.5-4 keV flux is 7.41 (-2.21/+2.90) erg cm^-2 s^-1. The uncertainties are at the 90% confidence level for the above parameters. Follow-up observations by EP-FXT has be scheduled. The optical follow-up observation was performed by MASTER-Net (Gress et al., GCN 45512). 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/45513. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...