TITLE:   GCN CIRCULAR
NUMBER:  45537
SUBJECT: GRB 260909A: Mondy optical observations and afterglow candidate
DATE:    26/09/09 16:14:01 GMT
FROM:    Nicolai Pankov at IKI <colinsergesen@gmail.com>

N. Pankov (IKI), E. Klunko (ISTP), A. Pozanenko (IKI),
A. Volnova (IKI), A. Moskvitin (SAO RAS) report on behalf of IKI-GRB-FuN:

We observed the field of GRB 260909A discovered by SVOM
(Saccardi et al., GCN 45534), and observed in optical by COLIBRI 
(Guan et al., GCN 45535) and Xinglong (Ma et al., GCN 45536), which resulted in upper limits. The observations were carried out using the 1.6-meter AZT-33IK telescope of Sayan Solar Observatory (Mondy) equipped with a CMOS photometer. A set of 38x120 sec images in the R band was obtained starting on 2026-09-09 at 13:44 UT (i.e. 2.446 hours since trigger).

In the coadd image we detect an uncatalogued object at coordinates (J2000) RA=00 52 08.462, Dec=+24 11 30.93 with a statistical uncertainty of 0.37 arcsec (66.7%).
The observation details and preliminary photometry is as follows:

Date,      UTstart  t-T0       Exp.  Filter Mag     Err.     UL
                    (mid,d)    (n*s)                       (3-sigma)

2026-09-09 13:44:47 0.12831  38*120  R      21.6    0.1      22.7

The preliminary photometry (Vega) is based on nearby USNO-B1.0 stars
and not corrected for the Galactic extinction. We suggest 
this uncatalogued source to be the GRB 260909A afterglow. We 
encourage further photometric follow-up of the SVOM/MXT field to verify 
this candidate source.