GCN Circular 41277
Subject
EP250807a: EP-WXT detection of a fast X-ray transient
Event
Date
2025-08-08T07:28:10Z (18 days ago)
Edited On
2025-08-08T14:11:28Z (18 days 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
EP250807a: EP-WXT detection of a fast X-ray transient
Y. Wang (PMO, CAS), Y. Q. Zhao (USTC,PRIC), H. Q. Cheng, Z. X. Ling (NAOC) on behalf of the Einstein Probe (EP) team:
We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250807a. The transient triggered EP-WXT (ID: 06800000803) at 2025-08-07T23:33:02 (UTC). The WXT position of the source is R.A. = 281.311 deg, DEC = 14.383 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The duration of the flare is about 250 seconds, with a peak flux of 2.08 x 10^-8 ergs/s/cm^2. The WXT spectrum during the flare can be fitted with an absorbed power-law model, yielding best-fit absorption column density of 0.80 (-0.26, +0.27) x 10^22 cm^-2 and photon index of 1.99 (-0.11, +0.14). The 0.5-4 keV unabsorbed flux is 7.14 (-1.59, +2.71) x 10^-9 ergs/s/cm^2.
Follow-up observations with several optical telescopes (Globus et al., GCN 41275; Kumar et al., GCN 41276) yielded only upper limits.
Follow-up observations with EP-FXT are scheduled.
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).