GCN Circular 45554
Subject
GRB 260909A: CrAO and AbAO optical upper limits
Event
Date
2026-09-11T20:58:57Z (3 days ago)
From
Nicolai Pankov at IKI <colinsergesen@gmail.com>
Via
Web form
N. Pankov (IKI), V. Rumyantsev (CrAO), R. Ya. Inasaridze (AbAO), M. Zhuzhunadze (AbAO),
A. Pozanenko (IKI), A. Volnova (IKI), A. Moskvitin (SAO RAS) and E. Klunko (ISTP) report on behalf of IKI-GRB-FuN:
We observed the field of GRB 260909A (discovered by SVOM, Saccardi et al., GCN 45534) in the optical R-band with the Shajn 2.6-meter telescope (ZTSh) of CrAO and the AS-32 0.7-meter telescope of AbAO. The observations started at both telescopes ~0.53 days since trigger. We do not detect any new optical sources in the EP-FXT localization circle (Mao et al., GCN 45543) in the co-add images from both telescopes.
The suggested source (Pankov et al., GCN 45537) is no longer considered as a candidate for the optical counterpart of GRB 260909A.
The observation details and preliminary upper limits are as follows:
Date UTstart t-T0 Exp. Filter UL Site/Telescope
(mid,d) (n*s) (3-sigma)
2026-09-09 22:44:16 0.53128 82*120 R 24.5 CrAO/ZTSh
2026-09-09 23:30:39 0.53744 89*60 R 21.2 AbAO/AS-32
The preliminary photometry (Vega) is based on nearby USNO-B1.0 stars
and not corrected for the Galactic extinction.
The result is an agreement with upper limits obtained by SVOM/C-GFT (Guan et al., GCN 45535),
Xinglong/2.16m (Ma et al., GCN 45536), Mondy/AZT-33IK (Pankov et al., GCN 45537),
SVOM/VT (Li et al., GCN 45539), ESO/VLT (Saccardi et al., GCN 45545),
OHP/T193 (Amram et al., GCN 45546), and LO/KAIT (Zheng et al., GCN 45549).