GCN Circular 41965
Z.P. Zhu (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), S.Y. Fu (HUST), 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 250920C (Fermi GBM team, GCN 41903; Gupta et al., GCN 41904; Mailyan & Meegan, GCN 41917; Gupta et al., GCN 41924; Wang et al., GCN 41929; Panteleeva et al., GCN 41957 ), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at New South Wales, Australia (SBO). Observations started at 18:21:14 UTC on 2025-09-20, i.e., ~ 2.9 hours after the Swift/BAT trigger and a series of frames in the R band were obtained.
The optical afterglow (Wortley et al., GCN 41907; Strausbaugh et al., GCN 41911; Ghosh et al., GCN 41913; Kuin et al., GCN 41920; Mohan et al., GCN 41925; Sanchez-Ramirez et al., GCN 41928; Guiffreda et al., GCN 41943; de Ugarte Postigo et al., GCN 41951; de Wet et al., GCN 41952; Izzo et al., GCN 41955; Zheng & Filippenko, GCN 41956; ) was clearly detected in our stacked R-band frame with a brightness of 18.87 +/- 0.02, calibrated with Pan-STARRS DR2 catalog and not corrected for Galactic extinction.