{
  "format": "text/markdown",
  "submitter": "SVOM_group <svomgroup@bao.ac.cn>",
  "subject": "GRB 260618B: LCO optical observations",
  "submittedHow": "web",
  "circularId": 45014,
  "createdOn": 1781946714006,
  "bibcode": "2026GCN.45014....1S",
  "body": "\nY.Y. Shi (GXU), A. Saccardi (CEA/Irfu), S.J.Yin (GXU), C. Wu (NAOC), L.P. Xin (NAOC), D. Turpin(CEA/Irfu) report on behalf of the SVOM mission team:\n \nWe observed the field of the GRB 260618B detected by Fermi-GBM (Fermi GBM team, GCN 44979; Veres et al. GCN 45010) and Fermi-LAT (Gupta et al., GCN 44983) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument.\n \nOur observation started on 2026-06-20 at 00:01:12 (about 31.1 hr after the trigger) and we obtained 5x200 s exposures in the SDSS r and 5x200 s exposures in the Pan-STARRS z filters.\n \nThe optical counterpart (Li et al., GCN 45001) is detected in our images. We measure the following magnitudes calibrated against the DESI DR10 catalog, and not corrected for Galactic extinction:\n \nr = 20.49 +/- 0.06 AB (mid-time 31.25 hr after the trigger);    \nz > 20.9 AB (3-sigma, mid-time 32.35 hr after the trigger).\n \nThis project is funded by the SVOM collaboration.\n",
  "eventId": "GRB 260618B"
}