TITLE:   GCN CIRCULAR
NUMBER:  45899
SUBJECT: GRB 261011A: LCO optical observations
DATE:    26/10/11 15:39:30 GMT
FROM:    luca.izzo@inaf.it

L. Izzo (INAF-OACn and DARK/NBI) reports on behalf of a larger collaboration:

We observed the field of GRB261011A (Cenko et al., GCN #45896) with the Sinistro instrument mounted on the 1-m telescope of the LCO network, located at Siding Spring, Australia. Observations started on 2026 October 11 at 14:25 UT (0.65 hr after the GRB trigger). We obtained a single image of 300s in the SDSS-g and SDSS-r filters.

We detect a bright source consistent with the position of the optical afterglow reported by Swift-UVOT (Cenko et al., GCN #45896) and by other ground-based facilities (O'Neill et al., GCN #45897; Fu et al., GCN #45898). We measure preliminary magnitudes of g = 20.01 +/- 0.02 mag and r = 19.47 +/- 0.02 (AB), calibrated against nearby stars from the Pan-STARRS catalog.

This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 101004719. We also acknowledge the use of the ECSnoopy package by E. Cappellaro.