{
  "createdOn": 1740939360008,
  "submitter": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
  "body": "Z.P. Zhu, S.Q. Jiang, X. Liu, J. An, S.Y. Fu, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report on behalf of a large collaboration:\n\nWe observed the field of EP250302a detected by Einstein Probe (Trigger ID: 01709132186), using the HMT-0.5m telescope located at Nanshan, Xinjiang, China. Observations started at 15:47:09 on 2025-03-02, i.e., 11.08 min after the EP trigger, and a series of unfiltered frames with different exposures were obtained.\n\nAn uncatalogued and varying optical source is detected within the EP/WXT error circle at coordinates\n\nR.A.(J2000) = 11:18:03.58\nDec.(J2000) = +33:35:09.06\n\nwith an uncertainty of ~0.5 arcsec. The source has R ~ 18.3 mag at a median time of 11.58 min after the EP trigger, calibrated with Legacy Survey DR10 and not corrected for Galactic extinction. We conclude that the source is the optical counterpart of EP250302a.\n\nObservations are still ongoing, and spectroscopy is encouraged.",
  "submittedHow": "web",
  "format": "text/plain",
  "eventId": "EP250302a",
  "bibcode": "2025GCN.39550....1Z",
  "circularId": 39550,
  "subject": "EP250302a: Nanshan/HMT optical counterpart detection"
}