TITLE: GCN CIRCULAR NUMBER: 44866 SUBJECT: GRB 260607A: TRT optical observations DATE: 26/06/08 10:34:45 GMT FROM: L. B. He at NAOC <helb@bao.ac.cn> L.B. He (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), J. An, X. Liu, Z.P. Zhu, S.Q. Jiang, L.B. He, D. Xu (NAOC), S.Y. Fu (HUST) report: We observed the optical counterpart candidate, AT2026ong, (Gompertz et. al., GCN 44864) of GRB 260607A detected by Fermi GBM (Fermi GBM Team, GCN 44855), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Fresno, California, U.S.A (SRO). A series of frames in the R-band were obtained. AT2026ong is clearly detected in our stacked image with a brightness of R = 19.2 +/- 0.2 at a median time of ~20.5 hrs post-trigger, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. There is no decay between the GOTO and TRT observations. The previously reported potential host galaxy of AT2026ong (Gompertz et. al., GCN 44864) has a redshift of z ~ 0.126 from the [REGALADE](https://vizier.cds.unistra.fr/viz-bin/VizieR-3?-source=J/A%2bA/706/A284/rega....) catalog (Tranin et al., 2026). View this GCN Circular online at https://gcn.nasa.gov/circulars/44866. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...