Year: 2026
Type: article
Abstract: The 44 cm Visible Telescope (VT) aboard the Space-based multi-band Variable Objects Monitor (SVOM) is a dual-band (400–650 nm and 650–1000 nm) instrument designed to detect and characterize the optical counterparts of gamma-ray bursts (GRBs) and other high-energy transients. This paper presents the VT’s design, scientific objectives, observing strategies, and both space- and ground-based data processing pipelines, along with its first-year in-orbit performance. In-orbit commissioning tests confirm a sensitivity of 22.5 AB mag (300 s exposure), extendable to ∼24 AB mag through stacking. This performance enables the VT to monitor over 100 GRBs in its first year with a remarkable ∼80% detection rate for SVOM/ECLAIRS-triggered bursts and ToO-observed bursts from other missions (e.g., Swift, Fermi, Einstein Probe), outperforming Swift/UVOT’s ∼40% detection rate. Beyond its high detection efficiency, the VT played a key role in identifying high-redshift GRBs-most notably GRB 250314A ( z = 7.3). Its deep upper limits at long wavelengths (up to 1 μ m) were pivotal in guiding follow-up observations with large ground-based telescopes, enabling crucial near-infrared detections for this burst. With its rapid response, deep sensitivity, and real-time processing capabilities, the VT is a key instrument for GRB research in SVOM-era, enabling critical studies of GRB optical afterglows, circumburst environments, relativistic jet dynamics, and the origins of optically dark bursts.
Authors: Yu-Lei Qiu, Li-Ping Xin, Jin-Song Deng, Jian Zhang, Xue-Wu Fan, Hong-Bo Cai, Chao Wu, Hua-Li Li, Rui-Feng Su, Qing-Yun Mao, Wei Gao, Gang-Yi Zou, Wei Wang, Zhu-Heng Yao, Dong Li, Kun Chen, Wen Chen, Yong-He Zhang, Xu-Hui Han, Jing Wang, Da-Wei Xu, Jesse T. Palmerio, Susanna. D. Vergani, Jian-Yan Wei, Bertrand Cordier
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Natural Science Foundation of China, Chinese Academy of Sciences, Centre National d’Etudes Spatiales, Nuclear Safety and Security Commission, Centre National de la Recherche Scientifique, Xi'an Institute of Optics and Precision Mechanics, National Astronomical Observatories, Chinese Academy of Sciences
OpenAlex ID: W7163009467