GCN Circular 43696

Subject

EP260210a: refined analysis of the EP-FXT observation

Event

EP260210a

Date

2026-02-11T14:20:01Z (a day ago)

Edited On

2026-02-12T13:46:40Z (2 hours ago)

From

EP Team at NAOC/CAS <ep_ta@bao.ac.cn>

Edited By

Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of EP Team at NAOC/CAS <ep_ta@bao.ac.cn>

Via

Web form

Z. H. Yang, R. Shi (PMO), Q. C. Zhao (IHEP), G. Y. Zhao (SYSU), Y. J. Zhang (THU) and Z. X. Ling (NAOC) on behalf of the Einstein Probe (EP) team:

The fast X-ray transient EP260210a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Shi et al., GCN 43681Loading...
 
 ). The refined analysis of the WXT data shows that the event started at T0=2026-02-10T10:20:58.53 (UTC), and lasted for approximately 220 seconds. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.6×10^20 cm^-2, and a photon index of 1.57 (-0.4/+0.4). The derived average unabsorbed 0.5-4 keV flux is 1.5 (-0.3/+0.4) × 10^(-10) erg/s/cm^2.
 
The Follow-up X-ray Telescope (FXT) on board EP autonomously observed this source a few minutes after the on board trigger. The FXT observation started at 2026-02-10T10:24:57 (UTC, T0+238 s). The effective exposure time of the observation is around 5 ks. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 169.8314, DEC = 45.3949 (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.6 × 10^20 cm^-2, and a photon index of 2.7 (-0.1/+0.1). The derived average unabsorbed 0.5-10 keV flux is 6.4 (-1.0/+1.0) ×10^(-13) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.

Further FXT follow-up observations have been arranged.

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).