TITLE:   GCN CIRCULAR
NUMBER:  40998
SUBJECT: GRB 250706A: SVOM/C-GFT upper limit in eary phase
DATE:    25/07/07 01:42:18 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

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) report on behalf of the SVOM/C-GFT team:

We observed the field of GRB250706A detected by Swift/BAT (GCN 40988) with LATIOS on SVOM/C-GFT.  Observations started at  2025-07-06T15:49:56 UTC, ~85 seconds after the trigger. 


A series of g, r, and i band images were obtained. No credible candidate was detected within the error box provided by XRT (GCN 40988) in our images after preliminary processing, the three sigma upper limits are:

| Date-Obs (mid-time) | Mid_t - T0 (s) | Exposure Time (s) | Band | Upper Limit (AB) |
|---------------------|----------------|-------------------|------|------------------|
| 2025-07-06T15:50:35 | 124            | 5×10              | i    | 19.31            |
| 2025-07-06T16:00:55 | 744            | 6×30              | g    | 20.66            |
| 2025-07-06T16:04:30 | 949            | 6×30              | r    | 20.37            |


The photometry was calibrated with nearby Pan-STARRS1 stars.


We thank the observation assistants Bowen Li & Yinhuai 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.