GCN Circular 42841
Subject
EP251124b follow-up observation by EP-FXT
Event
Date
2025-11-26T10:26:21Z (2 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
B. Zhang, J. P. Feng (USTC), D. F. Hu (PMO, CAS), H. Sun, H. N. Yang (NAO, CAS), Z. C. Zou (NJU) on behalf of the Einstein Probe (EP) team:
We performed a Target-of-Opportunity observation with the Follow-up X-ray Telescope on board the Einstein Probe (EP) for EP251124b (Feng et al, GCN 42834), which was also followed by Lipunov et al. (GCN #42835) and van Hoof et al. (GCN #42839). The observation began at 2025-11-25T22:12:00 (UTC) with an exposure time of about 1790 seconds. An uncatalogued X-ray source was detected within the WXT error circle at R.A. = 93.4802 deg, DEC = 52.7313 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. including both statistical and systematic uncertainties).
The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.5 x 10^21 cm^-2 and a photon index of 0.97 (-0.84, +0.93). The derived average unabsorbed 0.5-10 keV flux is 9.02 (-5.33, +13.9) x 10^(-13) erg/s/cm^2.
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).