TITLE:   GCN CIRCULAR
NUMBER:  45184
SUBJECT: GRB 260718A: LCO optical upper limits
DATE:    26/07/18 19:44:16 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

D. Turpin, A. Saccardi (CEA/Irfu), S.-J. Yin (GXU), C. Wu, L.-P. Xin (NAOC), W. Zhang (PMO), Y. Ma (NAOC)  report on behalf of the SVOM mission team:

We observed the field of GRB 260718A detected by SVOM (Antier et al., GCN 45177) and Fermi/GBM (Holzmann Airasca et al., GCN 45181) with the LCO 1m telescope at the Siding Spring Observatory (SAAO) equipped with the Sinistro instrument.

Our observation started at 2026-07-18T18:35:32 about 7.3 hours after the SVOM/ECLAIRs trigger time. We obtained 3x200 s exposures in the PanSTARRS z filters. 

No any uncatalogued source was identified in our stacked frames in the ECLAIRs localisation region as also reported by SVOM/VT (Ma et al., GCN 45178; Li et al., GCN 45179) and GRANDMA/KNC (Jacquesson et al., GCN 45180) .

We measure the following upper limits (5 sigma) calibrated against the SkyMapper DR4 catalog, and not corrected for Galactic extinction:

z = 20.1 (AB) T_mid - T0 = 7.4hr

This project is funded by the SVOM collaboration.