GCN 44918: GRB 260610B / AT2026owq: SAO RAS optical observations

2026-06-11T22:05:25.819Z | rev 0 | event: GRB 260610B

A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI),
A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team

We observed the field of GRB 260610B discovered by Fermi (The Fermi
GBM team, GCN 44891; GCN 44901) with the Zeiss-1000 1-m telescope
of SAO RAS equipped with the CCD photometer. The observations
carried out in BVRcIc filters starting June 11, 19:43:01 UT
(since ~ 1.4 days since trigger).

The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905;
Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al.,
GCN 44911; O'Neill et al., GCN 44914) is clearly detected in
our frames with the following brightness:

Date,      UTstart, t-T0,   Exp., Filter, Mag, Err., UL
                    (mid,d) (n*s)                    (3-sigma)
2026-06-11 19:43:01 1.40315 2*300 Rc      19.73 0.03 22.6

This preliminary photometry is based on nearby SDSS stars
(using Lupton 2005 transformation equations) and not corrected
for Galactic extinction. The observations are ongoing.