TITLE:   GCN CIRCULAR
NUMBER:  38133
SUBJECT: GRB 241108A: COLIBRÍ Upper Limits on the Optical Counterpart
DATE:    24/11/08 18:54:20 GMT
FROM:    Alan Watson at UNAM <alan@astro.unam.mx>

J.-G. Ducoin (CPPM), Francesco Magnani (CPPM), Alan M. Watson (UNAM),
S. Antier (OCA), Damien Dornic (CPPM), Stéphane Basa (UAR Pytheas),
William H. Lee (UNAM), D. Akl (AUS), Jean-Luc Atteia (IRAP), Nathaniel
R. Butler (ASU), Francis Fortin (IRAP), Simona Lombardo (LAM), 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 241108A detected by SVOM/ECLAIRs
(Sadibekova et al., GCN Circ. 38132) 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. Our field covers a 13 arcmin square region centered on the
ECLAIRS position and does not cover the whole uncertainty region.

In 9840 seconds of exposure from 2024-11-08 08:47 to 12:34 (1.63 to
5.41 hours after the trigger, we detect no sources other than those
previously identified in the PS1 or GAIA DR3 catalogs to a 5-sigma
limiting AB magnitude of:

r > 22.3

We warmly thank the COLIBRÍ engineering team and the staff of the
Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.
We warmly thank the GRANDMA IJCLAB team and S. Karpov for the access
of the STDWeb service for STDPipe.