TITLE:   GCN CIRCULAR
NUMBER:  44844
SUBJECT: GRB 260604C: LCO optical upper limit
DATE:    26/06/05 21:22:48 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud), S. Bisero (CEA/Irfu) report on behalf of the SVOM mission team:

We observed the field of GRB 260604C (Fermi GBM Team, GCN 44822; Gotz et al., GCN 44823) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument.

Our observation started on 2026-06-05 at 20:08:32 UT (about 1 day after the trigger) and we obtained 3x200 s exposures in the SDSS r filter.

In the stacked image we do not detect the optical counterpart (Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; Hellot et al., GCN 44835; Gompertz et al., GCN 44837; Gompertz et al., GCN 44843). We measure the following upper limit calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction:

r > 21.8 AB (3-sigma, mid-time 0.997 days after the trigger).

This project is funded by the SVOM collaboration.