GCN Circular 42937
Subject
EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
Event
Date
2025-12-02T03:28:01Z (18 hours ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. J. Zhang (THU), R. D. Liang (NAOC) Z. M. Wang (BNU), Y. Wu (NJU), H. N. Yang, H. Sun (NAOC) 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 EP251202a. The transient triggered EP-WXT (ID: 01709249064) at 2025-12-02T01:49:15 (UTC). The WXT position of the source is R.A. = 122.121 deg, DEC = 40.600 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The trigger time and the position of the transient is consistent with that of GRB 251202A detected by Fermi/GBM (GCN 42933).
We performed a follow-up observation with the Follow-up X-ray Telescope (FXT), starting at 2025-12-02T02:09:51 (UTC), about 20 minutes after the trigger. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 122.1190 deg, DEC = 40.6125 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). The position is 12 arcsec from the optical counterpart reported by Las Cumbres Observatory (Li et al., GCN 42934). 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).