TITLE: GCN CIRCULAR NUMBER: 41245 SUBJECT: GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/08/06 09:54:10 GMT FROM: F. Fortin at IRAP ffortin.sci.edu@gmail.com
Francis Fortin (IRAP), Camila Angulo (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Leonardo García García (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), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), W. J. Xie (NAOC), L. P. Xin (NAOC)
We imaged the field of the SVOM GRB 250806A (Xie et al., GCN Circ. 21243) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-08-06 07:59:05 to 08:58:07 UTC (from 51 seconds to 59 minutes after the onboard trigger) and obtained 2560 seconds of exposure in the i-band filter.
The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
In the stacked image, we do not detect any new source at the MXT source position (Xie et al., GCN Circ. 21243) down to the following 3-sigma limit:
i > 23.44
This result is consistent with the non detection reported by SVOM/VT (Wu et al. GCN Circ.41244).
Further observations and analysis are ongoing.
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.
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