TITLE: GCN CIRCULAR NUMBER: 39580 SUBJECT: EP250304a: Einstein Probe detection of an X-ray transient DATE: 25/03/04 02:35:25 GMT FROM: EP Team at NAOC/CAS ep_ta@bao.ac.cn

W. Chen, W. X. Wang (NAO, CAS), Y. J. Zhang (THU), C. Y. Dai (NJU), Y.Liu (NAO, CAS) report on behalf of the Einstein Probe 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 EP250304a. The transient triggered EP-WXT (ID: 01709132237 ) at 2025-03-04 01:32:30 (UTC). The WXT position of the source is R.A. = 208.394 deg, DEC = -42.818 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 cirlce, an uncatalogued X-ray source was detected at R.A. = 208.3965 deg, DEC = -42.8067 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).

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).

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