TITLE: GCN CIRCULAR NUMBER: 42345 SUBJECT: GRB 251018A: TRT optical afterglow detection DATE: 25/10/18 07:07:26 GMT FROM: L. B. He at NAOC <helb@bao.ac.cn> S.Y. Fu (HUST), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), Z.P. Zhu, L.B. He, X. Liu, J. An, S.Q. Jiang, D. Xu (NAOC) report on behalf of a large collaboration: We observed the field of GRB 251018A (Gupta et al., GCN 423243) using the 0.7-m telescope of the Thai Robotic Telescope (TRT) network, located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 2025-10-17 03:14:29.2 UT, i. e., 147 s after the trigger, and a series frames in the Sloan r filter were obtained. An uncatalogued and varying optical transient (OT) is clearly detected at the Swift-UVOT position (Gupta et al., GCN 42343), with r = 17.96 +/-0.03 (AB) at ~ 865 s post-burst, calibrated with nearby SKYMAPPER-DR2 catalog and without the Galactic extinction correction. We thus confirm that the OT is indeed the optical afterglow of the burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/42345. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...