TITLE:   GCN CIRCULAR
NUMBER:  45848
SUBJECT: GRB 261007A: SVOM/COLIBRÍ (FM-GFT) optical observations
DATE:    26/10/08 06:13:36 GMT
FROM:    Camila Angulo Valdez at UNAM <camiangulo@astro.unam.mx>

Camila Angulo (UNAM), Marion Guelfand (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (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), 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 imaged the field of the SVOM GRB 261007A (Goto et al., GCN Circ. 45824) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-10-08 04:57:06 to 05:41:53 UTC (from 22.5 to 23.45 hours after the trigger) and obtained 66 minutes of exposure in the r and z filters.

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.

We detected the optical counterpart (Zheng et al., GCN Circ. 45825; Saccardi et al., GCN Circ. 45829; Mohan et al., GCN Circ. 45832; Saccardi et al., GCN Circ. 45837; Shi et al., GCN Circ. 45838; An et al., GCN Circ. 45840; Arya et al., GCN Circ. 45841; Rehemtulla et al., GCN Circ. 45843; and Ruiz-Laguna et al., GCN Circ. 45844), at a preliminary magnitude of:

r = 21.65 +/-  0.03,
z = 21.32 +/- 0.08.

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.