GCN Circular 41879
Subject
EP250919a: Einstein Probe detection of an X-ray transient
Event
Date
2025-09-19T04:34:49Z (5 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. F. Liang (PMO), R. D. Liang, C. L. Guo, W. J. Hu, 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 EP250919a. The transient triggered EP-WXT (ID: 01709243841).
A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. At 2025-09-19T02:14:55 (UTC), an uncatalogued X-ray source was detected at R.A. = 298.5520 deg, DEC = -48.8395 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). An uncataloged optical source was detected within FXT error circle (GCN 41877, 41878). EP250919a is located within the 1-sigma error region of GRB 250919A (GCN 41874). However, the temporal offset exceeds 2 hours, and thus we cannot rule out the possibility of a chance spatial coincidence.
Further information will be updated when the telemetry data is received. Further follow-up observations are encouraged.
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).