TITLE: GCN CIRCULAR NUMBER: 43483 SUBJECT: GRB 260120B: SVOM/C-GFT optical counterpart detection DATE: 26/01/21 01:08:29 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> C. Wu (NAOC), Z. Kang (CHO), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 260120B detected by Fermi/GBM(Fermi GBM team, GCN 43477) and Swift/BAT (Ferro et al., GCN 43479) with LATIOS on SVOM/C-GFT. Observa-tions started at 2026-01-20T18:01:29 UTC, ~63 seconds after the trigger. An uncatalogued optical source, compared to Legacy Surveys DR10 Source Catalog, is detected in our images within the localization error circle (Ferro et al., GCN 43479) at: RA (J2000) = 18h58m38.35s = 284.65980 degrees Dec (J2000) = +61d54m18s = 61.90508 degrees with an uncertainty of ~0.5 arcsec. The magnitudes are: | Mid_t-T0(s) | exposure time (s) | band | mag (AB) | mag_err| |-------------|-------------------|------|----------|--------| | 68 | 1x10 | i | 15.74 | 0.04 | | 634 | 6x30 | g | 19.18 | 0.12 | | 854 | 6x30 | r | 19.03 | 0.12 | The brightness decays very rapidly, with the source fading by ~3.4 mag in the i band over 1000 s starting at T0+68 s. The photometry was calibrated against nearby stars in UCAC4 catalogue and no correction for Galactic dust extinction was applied. We thank the observation assistants Hong-Xv Xue and Bo-Wen Li 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43483. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...