TITLE: GCN CIRCULAR NUMBER: 38504 SUBJECT: GRB 241209A: COLIBRÍ Optical Upper Limit DATE: 24/12/09 21:59:11 GMT FROM: Damien Dornic ddornic@km3net.de
J.-G. Ducoin (CPPM), Francesco Magnani (CPPM), Damien Dornic (CPPM), Alan M. Watson (UNAM), Margarita Pereyra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), S. Antier (OCA), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Francis Fortin (IRAP) and Simona Lombardo (LAM), report:
We imaged the field of GRB 241209A detected by Swift/BAT and Fermi/GBM (GCN Circ. 38474, 38476, 38479) during the commissioning of the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.
The observations started 171 minutes after the GRB trigger. We observed with the engineering test camera in a red filter that approximates SDSS r. The data were reduced using custom software and then analysed and calibrated against the PS1 catalog using the STDWeb service (Karpov et al. 2022).
In 7680 seconds of exposure, we estimate an upper limit of 23.07 mag (3-sigma). This limiting magnitude is consistent with other optical observations of GOTO (Kumar et al, GCN Circ. 38481), MASTER (Lipunov et al., GCN Circ. 38483), VLT (de Ugarte Postigo et al, GCN Circ. 38484), REM (Brivio et al., GCN Circ. 38492) and GRANDMA/TAROT (Pillas et al., GCN Circ. 38500).
We warmly thank the COLIBRI engineering team and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.
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