TITLE: GCN CIRCULAR NUMBER: 43200 SUBJECT: EP251222a: Einstein Probe detection of an X-ray transient DATE: 25/12/23 03:34:27 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> Q. J. Huang, R. Shi (PMO, CAS), C. L. Guo (NAO, CAS), X. Mao (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 EP251222a. The transient triggered EP-WXT (ID: 01709250453) at 2025-12-22 15:18:06 (UTC). The WXT position of the source is R.A. = 62.519 deg, DEC = -1.506 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. = 62.5014 deg, DEC = -1.4795 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 are 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/43200. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...