TITLE:   GCN CIRCULAR
NUMBER:  43670
SUBJECT: GRB 260131A/B: continued Mondy optical observations
DATE:    26/02/09 15:13:09 GMT
FROM:    Alina Volnova at IKI RAS <alinusss@gmail.com>

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

We continued observations of the field of GRB 260131A/B (Fermi GBM Team,
GCN 43579; Sugai et al., GCN 43580; Roberts et al., GCN 43585; Frederiks et
al., GCN 43590; Luo et al., GCN 43591; Jiang et al., GCN 43600; Li et al.,
GCN 43605) with the AZT-33IK 1.5m telescope of the Mondy observatory on
Feb. 8 starting at 13:03:46 UT and taking several frames in R band. The
optical counterpart reported by Gompertz et al., GCN 43586; Lee et al., GCN
43587; Saccardi et al., GCN 43595; García García et al., GCN 43599, Shi et
al., GCN 43601; Sanchez-Ramirez et al., GCN 43604; Jayaraman et al., GCN
43606; Zhu et al., GCN 43607; Zheng et al., GCN 43609; Adami et al., GCN
43610; Volnova et al., GCN 43632 is detected in the stacked frame.
Preliminary photometry and observational details are the following:

Date           UT start  t-T0       Exp.    Filter Obj.    Err.   UL
Site/Telescope
                        (mid,days)  (n*s)                        (3sigma)
2026-02-08     13:03:46  8.30854    56*120  R      21.70   0.09   22.8
Mondy/AZT-33IK

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