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.