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GCN Circular 40941

Subject

EP250704a: Einstein Probe detection of an X-ray transient

Event

EP250704a

Date

2025-07-04T09:50:47Z (a day ago)

From

EP Team at NAOC/CAS <ep_ta@bao.ac.cn>

Via

Web form

A. Li (BNU), Y.H Cheng (SWIFAR,YNU), C. Zhou (HUST), G.Y. Zhao (SYSU), Y. J. Zhang (THU) and W. D. Zhang (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 EP250704a. The transient triggered EP-WXT (ID: 01709181144) at 2025-07-04T08:16:52 (UTC). The WXT position of the source is R.A. = 300.872 deg, DEC = 12.030 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. = 300.8742, DEC = 12.0243 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).

This transient is temporally coincidence with GRB 250704B (GCN 40940

). 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).