GCN Circular 42549
Subject
GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
Event
Date
2025-11-03T13:42:39Z (2 days ago)
From
Benjamin Schneider at MIT <bschn@mit.edu>
Via
Web form
Benjamin Schneider (LAM), Leonardo García García (UNAM), Stéphane Basa (UAR Pytheas), Jean-Grégoire Ducoin (CPPM), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), 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), Antonio de Ugarte Postigo (LAM), Y.-D. Hu (GXU) and X. Tian (GXU):
We imaged the field of the GRB 251103A (Hu et al., GCN Circ. 42534; Fermi GBM team, GCN 42536) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-11-03T10:17:32 to 11:26:49 UTC (from 5.52 to 6.67 hr after the trigger) and obtained 16 minutes of exposure in the g, r, i, z, and y filters.
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.
We detected the optical counterpart reported by Schneider et al., GCN Circ. 42535; Turpin et al., GCN Circ. 42538; Gritsevich et al., GCN Circ. 42539; Izzo et al., GCN Circ. 42540, O'Neill et al., GCN Circ. 42543, Ghosh et al., GCN Circ. 42545, at a preliminary magnitude of:
r = 19.48 +/- 0.04 (midtime = 6.04 hr)
z = 19.15 +/- 0.11 (midtime = 5.68 hr)
Compared to the early observations reported by Schneider et al. GCN Circ. 42535, we derive a temporal index of about -1.0 in the r-band.
Further observations are planned.
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.