{
  "subject": "EP261025a: Einstein Probe detection of a fast X-ray transient",
  "eventId": "EP261025a",
  "circularId": 46025,
  "format": "text/plain",
  "body": "G. J. Yang (NAO, CAS), S. Q. Zheng, J. R. Liu (BNU), Q. Y. Wu and Y. Liu (NAO, CAS), on behalf of the Einstein Probe (EP) team:\n\nWe report the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP261025a. The EP-WXT observation (ID: 08500000682) started at 2026-10-25T05:38:04 UTC, with an exposure time of 5605 s. The WXT light curve of the transient began at 2026-10-25T07:19:57.4 UTC and lasted for ~130 s. The WXT position of the source is R.A. = 2.554 deg, DEC = 60.763 deg (J2000) (l=117.917 deg, b=-1.707 deg) with an uncertainty of 2.22 arcmin in radius (90% C.L. statistical and systematic).\n\nWe fitted the WXT spectrum with an absorbed power-law model, fixing nH at the Galactic value 7.06e21 cm-2. We obtained a photon index of 1.6(-0.3/+0.3) and an unabsorbed flux of 2.6(-0.3/+0.3)e-9 erg/cm2/s during the flare. \n\nA follow-up observation with the Follow-up X-ray Telescope (FXT) was performed at 2026-10-25T13:13:55. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 2.5488 deg, DEC = 60.7658 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). \n\nFurther information will be updated when the telemetry data is received. Multi-wavelength observations are encouraged. \n\nLaunched on January 9, 2024, EP is a space X-ray observatory designed to monitor the soft X-ray sky with rapid X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE, and CNES.",
  "submittedHow": "web",
  "submitter": "EP Team at NAOC/CAS <ep_ta@bao.ac.cn>",
  "createdOn": 1792937323636,
  "eventType": [
    "X-ray Transient"
  ]
}