GCN Circular 40724
Subject
sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
Date
2025-06-13T20:05:07Z (2 days ago)
From
Alan Watson at UNAM <alan@astro.unam.mx>
Via
Web form
Alan M. Watson (UNAM), Rosa L. Becerra (U Roma), Enrique Moreno Méndez (UNAM), Sarah Antier (OCA), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Jerome Rodriguez (CEA):
We imaged the field of the SVOM X-ray transient sb25061218 (Rodriguez et al., GCN 40712) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-06-13 06:18 to 10:34 UTC (from 9.7 to 14.0 hours after the trigger) and obtained 112 minutes of exposure in the i 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 Pan-STARRS DR1 catalog, is on the AB scale, and is not corrected for Galactic extinction.
In the stacked image, we do not detect any new source within the ECLAIRs source region reported by Rodriguez et al. (GCN 40712) to a formal 10-sigma limit of:
i > 23.0,
although we note that this is roughly the 50% completion limit of the Pan-STARRS DR1 catalog used to identify new sources.
We also performed image subtraction against Pan-STARRS DR2 at the position of the two XRT sources 1 and 2 reported by Evans et al. (GCN Circ. 40721) and see no evidence for optical counterparts to the same limit.
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.