GCN Circular 45699
GRB 260922A: COLIBRÍ Optical Counterpart Candidate (correction to GCN 45698)
From: Camila Angulo Valdez at UNAM
Issued: 2026-09-23 05:54 UTC
Type: GRB, Optical Transient

Camila Angulo (UNAM), Marion Guelfand (CPPM), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM) report:

We re-analysed our images of the field of Swift GRB 260922A (Page et al., GCN Circ. 45690) previously reported by Angulo et al. (GCN Circ. 45698).

In the same stacked images, we detect an uncatalogued source consistent with the XRT error circle (Beardmore et al., GCN Circ. 45696) and not identified in the DESI Legacy Survey catalog (Dey et al. 2019) at:

RA(J2000) = 15:11:37.84 = 227.90767 degrees,
Dec(J2000) = +14:13:09.2 = +14.21923 degrees

with an uncertainty of 1 arcsec. The preliminary magnitude derived for that source is:

r = 22.44 +/- 0.13,

z = 22.35 +/- 0.25.

We suggest this is the optical counterpart of the GRB.

We apologize for the omission of this source in our previous GCN Circular.

We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM.

COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.

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.
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