GCN Circular 45235
Subject
EP260727a: Einstein Probe detection of an X-ray transient
Event
Date
2026-07-28T02:19:44Z (10 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
J. W. Hu (NAO, CAS) , H. C. Ding, T. Wu (AHNU), S. Q. Jiang, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team:
We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260727a. The transient triggered EP-WXT (ID: 01709276927) at 2026-07-27T20:37:57 (UTC). The WXT position of the source is R.A. = 346.455 deg, DEC = 3.240 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).
A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected by the onboard software at R.A. = 346.4623 deg, DEC = 3.1953 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic), which is consistent with the position of NOT likely optical counterpart (GCN 45234).
Further information will be updated when the telemetry data is received.
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).