GCN Circular 39420
Subject
EP250220a: EP-FXT follow-up observations
Date
2025-02-22T08:11:55Z (2 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
D. F. Hu (PMO, CAS), Y. L. Wang (NAOC, CAS), P. Y. Han, C. X. Zhang (HUST), B. B. Zhang (BNU), Y. Liu (NAOC, CAS) report on behalf of the Einstein Probe team:
Following the detection of the fast X-ray transient EP250220a (Wang et al., GCN 39387), we performed two follow-up observations with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission.
The first FXT observation started at 2025-02-20 14:59:57 (UTC), about 13 hours after the WXT detection, with an exposure of ~ 3 ks. Within the WXT error circle, one faint X-ray source was detected by one of the FXT modules, at the position of R.A. = 113.4516 deg, DEC = 39.8098 deg (J2000), with an uncertainty of 10 arcsec in radius (90% C. L. statistical and systematic). The detection is relatively weak and the spectrum is not well fitted.
The second FXT observation started at 2025-02-21 10:12:09 (UTC), about 32 hours after the WXT detection, with an exposure of ~ 7 ks. No source was detected within the WXT error circle. Assuming a photon index of 1.1 and Galactic absorption with NH = 7.13 x 10^20 cm^-2, we derive an upper limit of 1.90e-14 erg/s/cm^2 (0.5-10 keV; 90% C. L.).
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).