TITLE: GCN CIRCULAR NUMBER: 43696 SUBJECT: EP260210a: refined analysis of the EP-FXT observation DATE: 26/02/11 14:20:01 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> Z. H. Yang, R. Shi (PMO), Q. C. Zhao (IHEP), G. Y. Zhao (SYSU), Y. J. Zhang (THU) and Z. X. Ling (NAOC) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260210a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Shi et al., GCN 43681). The refined analysis of the WXT data shows that the event started at T0=2026-02-10T10:20:58.53 (UTC), and lasted for approximately 220 seconds. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.6×10^20 cm^-2, and a photon index of 1.57 (-0.4/+0.4). The derived average unabsorbed 0.5-4 keV flux is 1.5 (-0.3/+0.4) × 10^(-10) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP autonomously observed this source a few minutes after the on board trigger. The FXT observation started at 2026-02-10T10:24:57 (UTC, T0+238 s). The effective exposure time of the observation is around 5 ks. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 169.8314, DEC = 45.3949 (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.6 × 10^20 cm^-2, and a photon index of 2.7 (-0.1/+0.1). The derived average unabsorbed 0.5-10 keV flux is 6.4 (-1.0/+1.0) ×10^(-12) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Further FXT follow-up observations have been arranged. 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/43696. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...