TITLE:   GCN CIRCULAR
NUMBER:  38083
SUBJECT: GRB 241104A: COLIBRÍ Upper Limits on the Optical Counterpart
DATE:    24/11/05 13:37:47 GMT
FROM:    Alan Watson at UNAM <alan@astro.unam.mx>

Alan M. Watson (UNAM), Francis Fortin (IRAP), Stéphane Basa (UAR Pytheas),
William H. Lee (UNAM), S. Antier (OCA), D. Akl (AUS), Jean-Luc Atteia
(IRAP), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), J.-G. Ducoin
(CPPM), Simona Lombardo (LAM), Francesco Magnani (CPPM), and Margarita
Pereyra (UNAM)

SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang
(IHEP), Stéphane Basa (LAM), Jean-Luc Atteia (IRAP), Arnaud Claret (CEA),
Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Andrea
Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC),
En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing
Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (UNLV)

report:

We imaged the field of GRB 241104A detected by Fermi/GBM, SVOM/GRM,
SVOM/ECLAIRs, and EP/WXT (Fermi GBM Team, GCN Circ. 38075; Schanne et al.,
GCN Circ. 38078; SVOM/GRM Team, GCN Circ. 38082; Zhou et al., GCN Circ.
38081) during the commissioning of the COLIBRÍ (SVOM/F-GFT) telescope at
the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in
Mexico.

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 960 seconds of exposure from 2024-11-05 12:12 to 12:32 UTC (17.70 to
18.03 hours after the trigger), at high airmass, we detect no sources in
the ECLAIRs localization region other than those previously identified in
the PS1 or GAIA DR3 catalogs to a 5-sigma limiting AB magnitude of:

r > 20.8

We warmly thank the COLIBRÍ engineering team and the staff of the
Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.