GCN Circular 45253
Subject
EP260729a: Einstein Probe detection of an X-ray transient
Event
Date
2026-07-29T18:01:14Z (3 days ago)
Edited On
2026-07-29T20:27:20Z (3 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
H. Zhou (PMO, CAS), G. J. Yang, J. W. Hu, C. C. Jin (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 EP260729a. The transient triggered EP-WXT (ID: 01709277130) at 2026-07-29T17:04:47 (UTC). The WXT position of the source is R.A. = 357.559 deg, DEC = 26.992 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 at R.A. = 357.5308 deg, DEC = 26.9981 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).
Please note that an M4.0V C-type star, RX J2350.0+2659 (High Proper Motion Star), exists within the FXT error circle. Due to limited data, we cannot rule out the possibility that WXT was triggered by a stellar flare from RX J2350.0+2659.
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).