TITLE: GCN CIRCULAR NUMBER: 43093 SUBJECT: GRB 251214B: SVOM/C-GFT optical observations DATE: 25/12/14 11:59:55 GMT FROM: SVOM_group svomgroup@bao.ac.cn
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), Yulei Qiu(NAOC), Jing Wang (NAOC), Jinsong Deng(NAOC), Lei Huang(NAOC), Jianyan Wei (NAOC), report on behalf of the SVOM/C-GFT team:
We observed the field of GRB 251214B detected by Fermi/GBM (Fermi GBM team, GCN 43088) and Swift/BAT (Eyles-Ferris et al., GCN 43089) with LATIOS on SVOM/C-GFT. Observations started at 2025-12-14T09:12:24 UTC, ~10.12 min after the trigger.
The optical counterpart (Eyles-Ferris et al., GCN 43089) was clearly detected in our stacked images of band g, r , and i. The magnitudes are:
|[date-obs(mid-time)] | Mid_t-T0(min) | exposure time (s) | band | mag (AB) | mag_err| |--------------------|--------------|-------------------|------|----------|--------| |2025-12-14T09:12:42 | 10.75 | 3x10 | i | 16.56 |0.070| |2025-12-14T09:26:55 | 24.64 | 5x30 | g | 18.56 |0.090| |2025-12-14T09:40:03 | 37.77 | 6x30 | r | 18.33 |0.050|
The photometry was calibrated against UCAC4 catalogue and no correction for Galactic dust extinction was applied.
We thank the observation assistants Chun-Lei Guo and Yin-Huai Hao at Jilin observatory for their excellent support.
The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching.
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