TITLE:   GCN CIRCULAR
NUMBER:  38009
SUBJECT: GRB 241029A: COLIBRI Detection of the Optical Counterpart
DATE:    24/10/31 13:28:54 GMT
FROM:    Alan Watson at UNAM <alan@astro.unam.mx>

Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM),
D. Akl (AUS), S. Antier (OCA), Jean-Luc Atteia (IRAP), Nathaniel R. Butler
(ASU), Damien Dornic (CPPM), J.-G. Ducoin (CPPM), Francis Fortin (IRAP),
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 again the field of GRB 241029A detected by Fermi/GBM,
SVOM/ECLAIRs, and SVOM/GRM (Fermi GBM Team, GCN Circ. 37932; Schanne et
al., GCN Circ. 37956; Wang et al., GCN Circ. 37935) 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 4560 seconds of exposure from 2024-10-30 02:10 to 06:12 UTC (0.99 to
1.16 days after the trigger), we detect the optical counterpart (Jiang et
al, GCN Circ. 37937) with an AB magnitude of:

r = 21.78 +/- 0.15

This magnitude is consistent with the last optical observations reported
(Agui Fernandez et al., GCN Circ. 37950, Moskvitin et al., GCN Circ. 37954;
Qiu et al., GCN Circ. 37994).

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