GCN Circular 46083
Subject
GRB 261029A: SVOM/COLIBRÍ (FM-GFT) optical observations
Event
Date
2026-10-29T06:40:42Z (3 days ago)
From
Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa@lam.fr>
Via
Web form
Fredd Sánchez Álvarez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Camila Angulo (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Diego López-Cámara (UNAM), Nikos Mandarakas (LAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), Y.F. Liang (PMO) and Z.Y. Liu (GZNU) report:
We imaged the field of the SVOM GRB 261029A (Fermi GBM team, GCN Circ. 46071, and Goto et al., GCN Circ. 46072) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-10-29 01:45:00.61 to 2026-10-29 05:19:50.52 UTC (from 0.2989 to 3.8794 hours after the trigger) and obtained 24 minutes of exposure in the r filter.
The data were reduced and coadded with the ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
The source reported by O'Neill et al. (GCN Circ. 46073), He et al. (GCN Circ. 46078), Wang et al. (GCN Circ. 46079), De et al. (GCN Circ. 46080), Cotter et al. (GCN Circ. 46081), Yin et al. (GCN Circ. 46082) is very clearly detected and shows fading.
The preliminary magnitude measured in the first observation, obtained 0.3072 hours after the trigger, is:
r = 14.41 +/- 0.01
Further observations are ongoing.
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.