TITLE: GCN CIRCULAR NUMBER: 40051 SUBJECT: EP250404a: Einstein Probe detection of an X-ray transient DATE: 25/04/04 15:03:49 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> J. W. Hu (NAO, CAS), Q. C. Liu (THU), B. B. Zhang (BNU), Y. L. Hua (PMO, CAS), Y. Liu (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 EP250404a. The transient triggered EP-WXT (ID: 01709133918) at 2025-04-04T14:19:59 (UTC). The WXT position of the source is R.A. = 125.064 deg, DEC = 35.511 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. = 125.0575 deg, DEC = 35.5305 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). It is noted that EP250404a is temporally and spatially coincident with GRB 250404A (Fermi team, GCN Circ. 40050). 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/40051. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...