GCN Circular 45774
GRB 260924A: AbAO optical observations
From: Nicolai Pankov at IKI
Issued: 2026-09-28 08:59 UTC
Type: GRB, Optical Transient

N. Pankov (IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO), M. Zhuzhunadze (AbAO), A. Volnova (IKI), A. Moskvitin (SAO RAS) report on behalf of IKI-GRB-FuN:

We observed the field of a bright GRB 260924A (The Fermi GBM team, GCN 45712; D'Elia, GCN 45713; Salunke et al., GCN 45720; Holzmann Airasca et al., GCN 45721; Waratkar et al., GCN 45732; Yu et al., GCN 45741; Gupta et al., GCN 45750; Ridnaia et al., GCN 45751) at z=3.51 (Castro-Tirado et al., GCN 45740) with the AS-32 0.7m telescope of the Abastumani Astrophysical Observatory (AbAO) on 2 subsequent nights 2026-09-26 and 2026-09-27. The first observation has started at 00:31:30 UT, i.e, ~2 days since trigger. Both observations were taken in the R-band using a CCD-photometer. The optical afterglow (Hu et al., GCN 45717, Izzo et al., GCN 45718; Vijaykumar et al., GCN 45734; Klingler et al., GCN 45735; Ma et al., GCN 45736; Novotny et al., GCN 45743; Aryan et al., GCN 45748; Li et al., GCN 45728; Fortin et al., GCN 45759; Mo et al., GCN 45762) is detected in the co-add image of the first night, while absent in the second night co-add. Preliminary photometry and observation details are listed below:

Date UTstart Exptime t-T0 Filter OT Err. UL(3sigma)
(nxs) (days)
2026-09-26 00:31:30 68*60 1.99453 R 20.0 0.3 20.3
2026-09-27 00:16:21 90*60 2.99164 R n/d n/d 20.0

The photometry was calibrated using nearby stars from USNO-B1.0 (R2 magnitudes) and
has not been corrected for the Galactic extinction.

Filter: gamma-ray bursts are posted only if in the top 10% of the past year's — by fluence (total energy received per cm², from Fermi GBM, Konus-Wind, GECAM and similar circulars; now ≥ 3.9×10^-5 erg/cm²) or by the number of GCN Circulars about the burst (now ≥ 14). Thresholds are recalculated monthly.
Relayed automatically from NASA's General Coordinates Network.