GCN Circular 44816
Subject
EP260602a: EP-FXT follow-up observation
Event
Date
2026-06-04T07:09:04Z (2 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Z. X. Li, G. L. Huang, J. Y. Cao (IHEP, CAS), Y. Wang (PMO, CAS; UCB), G. J. Yang, W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team:
The X-ray transient EP260602a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Li et al., GCN 44770) at 2026-06-02T08:11:20 (UTC).
Follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2026-06-03T14:02:47(UTC), ~30 hours after the WXT detection. The exposure time of the observation is around 6 ks. The on-ground analysis of the FXT B data found an uncatalogued source at R.A. = 240.8343 deg, DEC = 50.4636 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is approximately consistent with the position of the optical counterpart (Xu et al., GCN 44781; Watson et al., GCN 44790; Malesani et al., GCN 44807). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 2.03×10^20 cm^-2, and a photon index of 1.6 (-0.9, +1.2). The derived average unabsorbed 0.5-10 keV flux is 7.1 (-4.3, +13.0) ×10^(-14) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.
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).