TITLE:   GCN CIRCULAR
NUMBER:  43770
SUBJECT: GRB 260208A: continued Mondy optical observations
DATE:    26/02/17 14:07:31 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; Mukherjee & Meegan, GCN 43673; Waratkar & Grefenstette, GCN 43674; Cheung et al., GCN 43675) at z = 2.36 (Dimple et al., GCN 43662) with the AZT-33IK 1.5m telescope of the Mondy observatory on Feb. 9 and 10 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; Volnova et al., GCN 43666; Pérez-Fournon et al., GCN 43694; Kuin & Cenko, GCN 43702) is detected in the stacked frame from Feb. 09, and is not detected on the next day.
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)
2026-02-09  17:00:51  1.51973   35*120  R      21.58  0.10  22.6    Mondy/AZT-33IK
2026-02-10  17:58:12  2.55608   30*120  R      n/d    n/d   22.6    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.