TITLE:   GCN CIRCULAR
NUMBER:  45588
SUBJECT: GRB 260915A: SVOM/C-GFT optical upper limits
DATE:    26/09/15 15:55:57 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

Y.Y. Shi (GXU), Z. Kang (CHO), C. Wu , 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), W.J. Tan (IHEP), Y.N. Ma (NAOC) report on behalf of the SVOM/C-GFT team:
 
 
We observed the field of GRB 260915A detected by SVOM/Eclairs (Liang et al., GCN 45570) with LATIOS on SVOM/C-GFT.Our observations started at 2026-09-15T11:54:07 UTC, ~ 10.7 hr after the trigger. 

We obtained follow-up imaging in g, r, and i bands. After preliminary analysis, no credible candidate was detected within the error box of source 1 provided by EP-FXT(Shi et al., GCN 45587) in our images. We measure the following upper limits calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction:

g > 20.8 AB (3-sigma, mid-time 11.89 hr after the trigger).
r > 19.9 AB (3-sigma, mid-time 11.36 hr after the trigger).
i > 21.0 AB (3-sigma, mid-time 10.83 hr after the trigger).

Our result is consistent with non-detection by Yin et al. (GCN 45573), Wu et al. (GCN 45575), Zhu et al. (GCN 45577), Perez-Garcia et al. (GCN 45578), Ducoin et al. (GCN 45580), Li et al. (GCN 45581), and Brivio et al. (GCN 45584). 

We note that in source 2 position of EP/FXT (Shi et al. GCN 45587), there is a known optical source (SDSS J003224.91+081258.0 : Quasar) ~0.1 mag brighter than the PS1 catalog value in the g,r, and i band.

We thank the observation assistants B.-W. Li  and  H.-X. Xue 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 arcmin x 21 arcmin 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.