GCN 44662: GRB 260509A: CrAO ZTSh optical upper limit

A. Moskvitin (SAO RAS), A. Pozanenko (IKI), V. Rumyantsev (CrAO),
N. Pankov (IKI), A. Volnova (IKI) report on behalf of IKI GRB-FuN.

We observed the field of the GRB 260509A (Götz et al., GCN 44504)
with the Shajn 2.6-meter telescope (ZTSh) of the Crimean Astrophysical
Observatory (CrAO). We obtained  40*120 s exposures R filter
on 2026-05-15 19:45:59--21:09:48 UT (5.94218 days after trigger).

We did not detect the OT (O'Neill et al., GCN 44505; Saccardi et al.,
GCN 44506; Wu et al., GCN 44507; Sánchez Álvarez et al., GCN 44509;
Zheng et al., GCN 44510; Kechin et al., GCN 44512; Belkin, GCN 44513;
Corcoran et al., GCN 44514; Bochenek and Perley, GCN 44516; Moskvitin
and Spiridonova, GCN 44563; Mo et al., GCN 44590; Li et al., GCN 44598)
down to the 3-sigma limiting magnitude of R_lim = 24.2.

This preliminary photometry is based on nearby stars from the USNO-B1
catalogue (R2 magnitudes) and is not corrected for the Galactic
extinction.