TITLE: GCN CIRCULAR NUMBER: 44841 SUBJECT: EP260602d: EP-FXT follow-up observation DATE: 26/06/05 12:47:27 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> J.Y. Cao, Z. X. Li, G. L. Huang, (IHEP, CAS), J. W. Hu, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP260602d was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Cao et al., GCN 44796) at 2026-06-02T21:13:25 (UTC). Follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2026-06-04T04:27:19(UTC), ~31 hours after the WXT detection. The exposure time of the observation is around 4 ks. The on-ground analysis of the FXT data found a source within the error circle of WXT at R.A. = 267.9681 deg, DEC = 18.1658 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic) which have no historical X-ray source within 10 arcsec. The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 6.7×10^20 cm^-2, and a photon index of 0.8 (-0.3, +0.4). The derived average unabsorbed 0.5-10 keV flux is 3.2 (-1.2, +1.8) ×10^(-14) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Since this source is below the RASS upper limit and shows no significant fading, we cannot identify it as the counterpart of EP260602d at present. The optical and infrared follow-up observations were performed by A. Aryan et al. (GCN 44813) and Tanishk Mohan et al. (GCN 44830) without detection. 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/44841. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...