{
  "circularId": 45417,
  "body": "Y.X Guan(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), Bertrand Cordier (CEA), Hatsune Goto (RIKEN, CEA) , report on behalf of the SVOM/C-GFT team:\n \nWe observed the field of GRB 260818B detected by SVOM/ECLAIRs (Bertrand Cordier et al., GCN 45398)， HXMT (Wang et al., GCN 45408), and SVOM/GRM (Ren et al., GCN 45411) with LATIOS on SVOM/C-GFT. Observations started at 2026-08-20T17:09:40.28 UTC, ~1.87 days after the trigger. \n \nWe obtained i-band follow-up imaging. After preliminary analysis, no credible candidate was detected within the error box provided by EP-FXT (Wu et al., GCN 45407) in our images. We measure the following upper limit calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction:\n\ni > 19.9 AB (3-sigma, mid-time 1.88 days after the trigger).\n\nThis is consistent with the non-detection reported by Shi et al.(GCN 45399) and Neill et al.(GCN 45403)\n\nWe thank the observation assistants Y.-H. Hao and C.-L. Guo at Jilin observatory for their excellent support.\n \nThe 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.",
  "submittedHow": "web",
  "submitter": "SVOM_group <svomgroup@bao.ac.cn>",
  "createdOn": 1787329284369,
  "format": "text/plain",
  "eventId": "GRB 260818B",
  "subject": "GRB 260818B: SVOM/C-GFT optical upper limit",
  "eventType": [
    "GRB",
    "Optical Transient"
  ]
}