AT2026cex (LFBOT ATeL#17646): COLIBRI and C-GFH detection of quasi-periodic photometric modulation
ATel #17662; Margarita Pereyra (UNAM), Chao Wu (NAOC), Stephane Basa (UAR Pytheas), Z. Kang (CHO), William H. Lee (UNAM), J. Y. Wei (NAOC), Edilberto Aguilar-Ruiz (UNAM), Dalya Akl (NYUAD), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Jean-Luc Atteia (IRAP), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), J. S. Deng (NAOC), Damien Dornic (CPPM), Jean-Gregoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo Garcia Garcia (UNAM), Ramandeep Gill (UNAM), Noemie Globus (UNAM), X. H. Han (NAOC), L. Huang (NAOC), Asuka Kuwata (UNAM), X. M. Lu (NAOC), Z. W. Li, Y. Lv (CHO), Nikos Mandarakas (LAM), Diego Lopez-Camara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Mendez (UNAM), Y. L. Qiu (NAOC), Ny Avo Rakotondrainibe (LAM), Fredd Sanchez Alvarez (UNAM), Benjamin Schneider (LAM), Damien Turpin (CEA-Irfu), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), J. Wang, Y. J. Xiao, L. P. Xin , P. P. Zhang, R. S. Zhang (NAOC), report:
on 10 Feb 2026; 01:40 UT
Credential Certification: Margarita Pereyra (mpereyra@astro.unam.mx)
Subjects: Optical, Binary, Transient, Variables
We observed the field of the AT2026cex, the candidate LFBOT reported by Tsuboi, Nakaoka, & Kawabata (ATeL #17646) and followed up by Gill et al. (ATel #17647), Pereyra et al. (ATel #17648), Schneider et al. (ATel #17649), Sun et al. (ATel #17651), Ma et al. (ATel #17652), and Perez-Fournon et al. (ATel #17660), with the DDRAGO wide-field imager on the COLIBRI telescope at the Observatorio Astronomico Nacional on the Sierra de San Pedro Martir, Mexico, and the SVOM/C-GFT telescope with the LATIOS camera at Jilin Station, Changchun Observatory, China on the nights of 2026-02-06 to 2026-02-09.
During our jointly conducted observations, we clearly observe a quasi-periodic modulation of the light curve in the different photometric bands, g, r, i, z, and y with a characteristic time of approximately 1.35 hours.
This timescale is typical for certain classes of accreting binary stars. It suggests that the underlying star Gaia 866940901044573184 was previously seen in a quiescent state but is now undergoing an outburst.
Further observations and analysis are ongoing.
We thank the staff of the Observatorio Astronomico Nacional on the Sierra de San Pedro Martir and the COLIBRI and DDRAGO engineering teams.
COLIBRI is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronomico Nacional on the Sierra de San Pedro Martir, Baja California, Mexico.
The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching.
