GCN Circular 42613
Subject
GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
Event
Date
2025-11-07T14:32:43Z (a day ago)
From
F. Fortin at IRAP <ffortin.sci.edu@gmail.com>
Via
Web form
Francis Fortin (IRAP), Camila Angulo (UNAM), Jean-Luc Atteia (IRAP), Benjamin Schneider (LAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM) report:
We imaged the field of the SVOM GRB 251106A (Antier et al., GCN Circ. 42605) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed a second epoch from 2025-11-07 12:34 to 12:50 UTC (from 16.63 to 16.89 hours after the trigger) and obtained an additional 16 minutes of exposure in the r filter at high airmass (3 to 3.5).
The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
We detect the optical counterpart we previously reported (Angulo et al, GCN Circ. 42607) at the following preliminary magnitude:
r = 21.85 +/- 0.13
Our photometry shows clear fading with respect to our earlier epoch, confirming that this is the optical counterpart of the GRB.
We note that the position of the afterglow optical counterpart is coincident with a faint source in the Legacy Survey (Dey et al. 2019) at r = 22.56 +/- 0.17, which could be the host galaxy of the GRB.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.
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.