TITLE: GCN CIRCULAR NUMBER: 45480 SUBJECT: EP260830a: EP-WXT detection of a fast X-ray transient DATE: 26/09/01 06:21:48 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> X. Mao (NAO, CAS), Y. F. Liang, J. Y. Liu (PMO), Q. H. Lao, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient, designated EP260830a (notice ID: 01709295827), 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 about 2026-08-30T15:30:23(UTC) and lasted for about 500s. The position of the transient is R.A. = 2.055 deg, Dec. = 16.919 (J2000), with an uncertainty radius of 2.4 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 4.21×10^20 cm^-2 and a photon index of 1.03 (-0.92/+1.02). The derived average unabsorbed 0.5-4 keV flux is 3.69 (-1.65/+2.93) x 10^(-11) 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/45480. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...