GCN Circular 43941

Z. Kang(CHO), C. Wu (NAOC), 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), F. Mag-nani, A. Foisseau (CPPM) report on behalf of the SVOM/C-GFT team:

We observed the field of GRB 260307B detected by SVOM/ECLAIRs (Magnani et al. GCN 43940

) with LATIOS on SVOM/C-GFT. Observations started at 2026-03-07T13:47:15 UTC, ~109 seconds after the trigger.

We obtained i-band follow-up imaging. The target had a very low elevation. After preliminary analysis, no credible candidate was detected within the error box provided by SVOM/MXT (Magnani et al., GCN 43940

) in our images.

The 5-sigma upper limits are:

i > 19.7 mag (AB) (5-sigma, mid-time 7.7 min after the trigger)

The photometry was calibrated against the UCAC4 catalogue, and no correction for Galactic dust extinction was applied. Further observations and analyses are ongoing.

We thank the observation assistants Chun-Lei Guo and Ying-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.