TITLE: GCN CIRCULAR NUMBER: 40186 SUBJECT: GRB 250419A: SVOM/C-GFT optical observations DATE: 25/04/20 14:49:06 GMT FROM: SVOM_group GRB 250419A: SVOM/C-GFT optical observations Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei, Qiu(NAOC), Jing Wang (NAOC), Jinsong Deng(NAOC), Lei Huang(NAOC), Jianyan Wei (NAOC), B.-T. Wang (YNAO, CAS), Y.H. Cheng (SWIFAR,YNU) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 250419A detected by SVOM/ECLAIRs (sb25041901, Wang et al., GCN 40168) with C-GFT. Our observations were started on 2025-04-19T13:08:53 UTC, ~10.66 hr after the trigger. The optical counterpart (reported by Ocelotl López et al. GCN 40169, Xin et al. GCN 40170, Zheng et al. GCN 40171, Kumar et al. GCN 40172, Lipunov et al. GCN 40179, Odeh et al. GCN circ. 40180, Perley and Bochenek GCN circ. 40181, Pankov et al. GCN 40182, and Pérez-Fournon et al. GCN 40183, Kuin et al. GCN 40185) was detected in the stacked g, r, and i-band images. The results are, (T-T0)_mid(sec) exptime(s) mag mag_err band ----------------------------------------------- 46935 10x30s 19.38 0.17 r 47723 10x30s 19.25 0.21 i 49013 10x30s 19.98 0.22 g The photometry was calibrated with nearby UCAC4 stars. Further analysis is on-going. We thank the observation assistants Shuai Liu 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.