GCN Circular 37967
Subject
EP241026b: EP-FXT follow-up observation
Date
2024-10-30T13:14:26Z (24 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
T.Y. Lian, Y. L. Wang, D. Y. Li, S. X. Wen, W. Yuan (NAO, CAS) on behalf of the Einstein Probe team
Following the detection of the fast X-ray transient EP241026b (Lian et al., GCN 37902), we performed an observation of EP241026b with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe. The observation started at 2024-10-27T03:36:23 (UTC), about 9 hours after the EP-WXT detection, with an exposure time of 4037 seconds. An uncatalogued X-ray source is detected at R.A. = 56.4058 deg, DEC = 41.0312 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The average FXT spectrum in 0.5-10 keV band can be fitted by an absorbed power law with a photon index of 2.3(+1.5/-1.4) (with a column density fixed at the Galactic one of 3.38 x 10^21 cm^-2), giving an average unabsorbed flux of 1.5(+2.8/-0.5) x 10^-13 erg/s/cm^2 in the 0.5-10 keV band. The FXT position is 2 arcsec away from the likely optical counterpart detected by LBT (Rossi et al., GCN 37938). We thus consider that the FXT detection is the X-ray counterpart of EP241026b.
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).