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 View this GCN Circular online at https://gcn.nasa.gov/circulars/38009. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...