TITLE:   GCN CIRCULAR
NUMBER:  43567
SUBJECT: GRB 260128B: LCO optical upper limits
DATE:    26/01/30 09:25:29 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

C. Wu (NAOC), J. X. Cao (GXU), A. Saccardi (CEA/Irfu), D. Turpin (CEA/Irfu), report on behalf of the SVOM mission team:

We observed the field of the SVOM GRB 260128B (Brunet et al., GCN 43561) with the LCO 1m telescope at Cerro Tololo Interamerican Observatory equipped with the Sinistro instrument.

Our observation started on 2026-01-30 at 00:48:11 UT (about 1.75 days after the trigger) and we obtained 6x300 s exposures in the SDSS r and 5x300 s exposures in the Pan-STARRS z filters. In the stacked image, we do not detect any new source within the SVOM/ECLAIRs error box, in agreement with Méndez et al. (GCN 43566).

We measure the following upper limit calibrated against the PanSTARSS DR1 catalog, and not corrected for Galactic extinction:

r > 22.4 AB (3-sigma, mid-time 42.5 hr after the trigger)
z > 21.3 AB (3-sigma, mid-time 42.2 hr after the trigger).

This project is funded by the SVOM collaboration.