TITLE: GCN CIRCULAR NUMBER: 45263 SUBJECT: EP260731a: NOT optical upper limit DATE: 26/07/31 04:39:27 GMT FROM: liuxing@nao.cas.cn 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: We 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. No 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/45263. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...