GCN Circular 44802
Subject
EP260602b: EP-FXT follow-up observation
Event
Date
2026-06-03T13:21:53Z (3 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
J. W. Hu (NAO, CAS), Z. X. Li, G. L. Huang, J. Y. Cao (IHEP, CAS), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team:
The X-ray transient EP260602b was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Hu et al., GCN 44786) at 2026-06-02T17:53:12 (UTC).
Follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2026-06-03T04:30:31(UTC), ~10.5 hours after the WXT detection. The exposure time of the observation is around 4 ks. The on-ground analysis of the FXT data found an uncatalogued source at R.A. = 273.4737 deg, DEC = 7.5702 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent with the position of the optical counterpart (He et al., GCN 44780). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.9×10^21 cm^-2, and a photon index of 2.0 (-0.7, +0.8). The derived average unabsorbed 0.5-10 keV flux is 1.4 (-0.6, +1.1)×10^(-13) 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).