TITLE:   GCN CIRCULAR
NUMBER:  43666
SUBJECT: GRB 260208A: Mondy optical observations
DATE:    26/02/09 11:57:27 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 observed the field of GRB 260208A (Fermi GBM team, GCN 43635; Sonawane et al. 2026, GCN 43642; Longo et al. 2026, GCN 43645; Dichiara et al. 2026, GCN 43652; Luo et al. 2026, GCN 43658) at z = 2.36 (Dimple et al., GCN 43662) with the AZT-33IK 1.5m telescope of the Mondy observatory on Feb. 8 starting at 20:54:02 UT and taking several 120-seconds frames in the R band. The optical counterpart (Lipunov et al., GCN 43640; Wortley et al., GCN 43641; Dichiara et al., GCN 43652; Ma et al., GCN 43655; Ahumada et al., GCN 43657; Dimple et al.,GCN 43661; Magnani et al., GCN 43664; Gupta et al., GCN 43665) is detected in the single 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     20:54:02  0.66429    10*120  R      19.92   0.06   21.8     Mondy/AZT-33IK
2026-02-08     21:14:03  0.67819    10*120  R      20.14   0.07   21.8     Mondy/AZT-33IK
2026-02-08     21:34:04  0.69139    10*120  R      20.05   0.06   21.8     Mondy/AZT-33IK

The photometry is based on nearby SDSS stars (R-magnitudes obtained using the 2005 Lupton transformation equations) and is not corrected for Galactic extinction.