TITLE:   GCN CIRCULAR
NUMBER:  45014
SUBJECT: GRB 260618B: LCO optical observations
DATE:    26/06/20 09:11:54 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>


Y.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:
 
We 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.
 
Our 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.
 
The 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:
 
r = 20.49 +/- 0.06 AB (mid-time 31.25 hr after the trigger);    
z > 20.9 AB (3-sigma, mid-time 32.35 hr after the trigger).
 
This project is funded by the SVOM collaboration.