TITLE: GCN CIRCULAR NUMBER: 35396 SUBJECT: GRB 231216A: Nanshan/HMT optical upper limit DATE: 23/12/18 14:59:03 GMT FROM: Dong Xu at NAOC/CAS <dxu@nao.cas.cn> J. An, S.Y. Fu, S.Q. Jiang, X. Liu, Z.P. Zhu, T.H. Lu, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report: We observed the field of GRB 231216A detected by Swift (Sbarrato et al., GCN 35378) using the HMT-0.5m telescope located at Nanshan, Xinjiang, China. Observations started at 18:42:32 UT on 2023-12-16, i.e., 6.83 mins after the Swift/BAT trigger, and a series of 20, 40, 60, 90, 120, 200 s frames were obtained without any filter. No optical source is detected in our stacked image at the XRT position (Sbarrato et al., GCN 35378), down to the 3-sigma limiting magnitude of m(r) > 20.2 mag (AB) @ 26.03 mins post-burst, calibrated with the nearby PanSTAR field in the Sloan r-filter. The magnitude is not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/35396. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...