TITLE: GCN CIRCULAR NUMBER: 43521 SUBJECT: EP260126a: NOT optical observations DATE: 26/01/27 04:35:07 GMT FROM: Dong Xu at NAOC/CAS <dxu@nao.cas.cn> Z.P. Zhu, J. An, X. Liu, S.Q. Jiang, L.B. He, D. Xu (NAOC), S.Y. Fu (HUST), J.P.U. Fynbo (DAWN/NBI), S. Bijavara (NOT) report on behalf of a large collaboration: We observed the field of EP260126a (Fu et al., GCN 43520) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 22:13:05 UT on 2026-01-26, i.e., 17.8 hr after the EP trigger, and we obtained 5 x 180 s frames in the Sloan r-band and 5 x 200 s frames in the Sloan z- band. No new optical source is detected within the EP/FXT error circle (Fu et al., GCN 43520), down to 5-sigma upper limits of r ~ 23.6 and z ~ 22.5, calibrated with nearby Pan-STARRS stars and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43521. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...