Speaker
Description
Blazars, a subclass of active galactic nuclei, possess relativistic plasma jets aligned close to the line of sight of the observer and exhibit broadband emission from radio to gamma-ray energies. However, the jet launching mechanism, particle acceleration processes, and the origin of high-energy emission are still not fully understood. In this study, we focus on OP 313, a flat-spectrum radio quasar (FSRQ). OP 313 is the most distant blazar detected in very-high-energy (VHE; >100 GeV) gamma rays. It has been observed by LST-1 of the Cherenkov Telescope Array Observatory (CTAO) in December 2023, and multiple gamma-ray flares have also been detected by Fermi-LAT. These properties make it an excellent target for investigating the high-energy emission mechanisms. We conducted a long-term monitoring observation from November 2023 to July 2025 using the Kanata telescope at Higashi-Hiroshima Observatory. Photometric and polarimetric observations were performed in the optical and near-infrared bands simultaneously with the HONIR instrument mounted on the Kanata telescope. We also carried out spectral energy distribution (SED) modeling with multi-wavelength data; Fermi/LAT, Swift/XRT/UVOT, Kanata/HONIR. As a result, the observed data can be well reproduced by a two-zone leptonic model. In this presentation, we discuss the high-energy emission mechanisms based on the spectral variability revealed by the long-term observations.
