{
  "eventId": "EP250321a",
  "submitter": "sqjiang at NAOC <sqjiang@bao.ac.cn>",
  "createdOn": 1742546346591,
  "circularId": 39804,
  "submittedHow": "web",
  "body": "S.Y. Fu (HUST), W.X. Li, J. An, S.Q. Jiang (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), X. Liu, Z.P. Zhu, Z. Fan, N.C. Sun, D. Xu, Y.N. Wang (NAOC) report on behalf of a large collaboration:\n\nWe observed the field of EP250321a detected by EP/WXT (Hu et al., GCN 39800) using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Sierra Remote Observatories in California. We obtained several 300 s frames in the R and I filters.\n\nAn uncatalogued and decaying optical source is detected within the error circle at coordinates\n\nR.A. (J2000) = 11:57:03.02\nDec. (J2000) = +17:21:45.94\n\nwith an uncertainty of ~0.5 arcsec. The source has R ~ 19.7 mag at 1.24 hr and I ~ 18.8 mag at 1.72 hr after the EP trigger, calibrated with nearby Pan-STARRS DR2 stars and not corrected for Galactic extinction.\n\nWe think that the source is very likely the optical counterpart of EP250321a.",
  "format": "text/plain",
  "bibcode": "2025GCN.39804....1F",
  "subject": "EP250321a: TRT optical counterpart detection"
}