{
  "submitter": "liuxing@nao.cas.cn",
  "submittedHow": "web",
  "format": "text/plain",
  "circularId": 45263,
  "body": "X. Liu, J. An, Z.P. Zhu, S.Q. Jiang, L.B. He, D. Xu (NAOC), S.Y. Fu (HUST), J. P. U. Fynbo (DAWN/NBI), A. L. Bouquin, A. Schenone-Zanuzzi (NOT) report:\n \nWe observed the field of EP260731a detected by EP (Ni et al., GCN 45261), using the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observation started at 2026-07-31 03:16:25.90 UT, i.e., 2.37 hours post-trigger, and a series of z-band frames were obtained. The target was 16 deg from the moon at 98% illumination at the time of the observation.\n\nNo uncatalogued optical transient is detected in the stacked image within the EP-FXT error circle (Ni et al., GCN 45261) down to a 5-sigma limiting magnitude of z ~ 19.8 at a median time of 2.46 hr post-trigger, calibrated with Pan-STARRS DR2 stars in the field.",
  "subject": "EP260731a: NOT optical upper limit",
  "eventType": [
    "X-ray Transient"
  ],
  "eventId": "EP260731a",
  "bibcode": "2026GCN.45263....1L",
  "createdOn": 1785472767309
}