GCN Circular 45631
Subject
GRB 260917B: Mondy optical upper limit
Event
Date
2026-09-18T13:51:45Z (3 days ago)
From
Alina Volnova at IKI RAS <alinusss@gmail.com>
Via
Web form
A. Volnova (IKI), E. Klunko (ISTP), A. Pozanenko (IKI), A. Moskvitin (SAO), N. Pankov (IKI) report on behalf of IKI-GRB-FuN:
We observed the field of the GRB 260917B detected by SVOM/ECLAIRs (sb26091701; He et al., GCN 45606) with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) starting on 17 Sep, 2026, at 19:39 UT (i.e., ~16h after the trigger).
The optical counterpart reported previously by SVOM/COLIBRÍ (Dornic et al., GCN 45607) and observed by other facilities (Ma et al., GCN 45610; Yin et al., GCN 45608; Mohan et al., GCN 45611; Jelinek et al., GCN 45617) is not 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)
2026-09-17 19:39:51 0.67396 21*120 R n/d n/d 21.5 Mondy/AZT-33IK
The photometry (Vega) is based on several nearby PS1-DR2 stars (R-magnitudes Lupton's transformation) and is not corrected for the Galactic extinction.