TITLE: GCN CIRCULAR NUMBER: 38546 SUBJECT: GRB 241212A : SVOM/C-GFT optical upper limit at early phase DATE: 24/12/13 00:58:36 GMT FROM: Chao Wu at NAOC <cwu@nao.cas.cn> SVOM/C-GFT team: Zhe Kang (CHO), Chao WU (NAOC), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC) SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC),Olivier Godet (IRAP), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Shao-Lin Xiong (IHEP), Bing Zhang (UNLV) We observed the field of GRB 241212A (Zhang et. al, GCN 38541; Fermi team GCN 38540;Joshi et al. GCN 38544) starting at 2024-12-12T09:22:45 UT, ~53 sec after the burst trigger with C-GFT. A series of g, r and i band images were obtained with exposure time of 10s. Due to bad observation condition(not good weather, low altitude and ~13.8 deg to the moon), the optical counterpart reported by Qiu et al. (GCN 38545) was not detected in the images. The upper limit at early phase are, (T-T0)_mid(sec) limiting_mag(3sigma) ------------------------------------- 58 15.80 91 16.80 The photometry was calibrated with nearby stars in ucac4. We thank the observation assistant Bowen Li and Chunlei Guo at Jilin observatory for their excellent support. Chinese Ground Follow-up Telescope of SVOM mission is located at Jilin, Changchun Observatory, National Astronomical Observatories, CAS. It has FOV of 1.28 deg x 1.28 deg with a 4k*4k CMOS detector mounted on the primary focus of 1.2-meter-aperure telescope. View this GCN Circular online at https://gcn.nasa.gov/circulars/38546. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...