GCN Circular 44872
C. Wu (NAOC), Z. Kang (CHO), L.P. Xin（NAOC), S.J. Yin (GXU), 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), N. Dagoneau, S. Bisero (CEA Saclay) report on behalf of the SVOM/C-GFT team:
We observed the field of GRB 260604C (SVOM burst-id sb26060404) detected by SVOM/ECLAIRs (GCN 44823) with LATIOS on SVOM/C-GFT. Observations started at 2026-06-05T15:54:29 UTC, ~19.54 h after the trigger.
We obtained 9X90s exposures in the SDSS g filter. After preliminary analysis，we do not detect the optical counterpart (Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; Hellot et al., GCN 44835; Gompertz et al., GCN 44837; Gompertz et al., GCN 44843; Saccardi et al., GCN 44844; Chen et al., GCN 44851; Moskvitin et al., GCN 44852; Sasaki et al., GCN 44857 ; Pankov et al., GCN 44858 ; Pankov et al., GCN 44862 ; Burkhonov et al., GCN 44865 ) in the stacked image. The upper limit is measured as follows:
g > 21.1 AB (3-sigma, mid-time 19.68 h after the trigger).
The photometry was calibrated against Pan-STARRS1 DR1 catalog and no correction for Galactic dust extinction was applied.
We thank the observation assistants Hong-Xu 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.