Multiwavelength quasi-periodic variability of the blazar Ton 599

Sotnikova Yu V.; Mufakharov T. V.; Volvach A. E.; Vlasyuk V. V.; Khabibullina M. L.; Mikhailov A. G.; An T.; Kudryavtsev D. O.; Kovalev Yu A.; Kovalev Yu Yu; Popkov A. V.; Savchenko S. S.; Erkenov A. K.; Morozova D. A.; Semenova T. A.; Spiridonova O. I.; Kharinov M. A.; Rakhimov I. A.; Andreeva T. S.; Cui L.; Wang X.; Chang N.; Udovitskiy, R. Yu ; Zhekanis P. G.; Borman G. A.; Grishina T. S.; Kopatskaya E. N.; Larionova E. G.; Troitskiy I. S.; Troitskaya Yu V.; Vasilyev A. A.; Zhovtan A. V.; Kratov D. V.; Volvach L. N.; Shishkina E. V.; Dmytrotsa A. I.; Zharov, V. I.

During the last 40─50 yr, the TeV blazar Ton 599 has systematically experienced major outbursts detected in a wide wavelength range from radio to  γ-rays. In this work, we present an analysis of Ton 599 quasi-periodic variability across multiple wavelengths using an observing baseline from 1983 to 2025. The  γ-ray, optical, and radio emissions are found to be highly correlated with time lags  ∼0─360 d, which indicates that they are triggered by the same population of particles. Using the Lomb─Scargle periodogram and the Weighted Wavelet Z-transform, we revealed several periodic components with characteristic periods of 1.4, 1.7, 2.3, 6.5, and 7.5 yr. The result is consistent with the detection of periodic components in the 1997─2011 light curves, which means that we observe the same mechanism causing long-term periodic variability. A model of a binary supermassive black hole (SMBH) with a precessing jet, applied to the radio light curves of Ton 599, yields frequency-dependent best-fitting parameters with orbital periods ranging from  ∼ 1.2 to 1.7 yr and precession periods from  ∼ 5.8 to 7.7 yr. This result implies the existence of an SMBH system modulating emission through both the orbiting and jet precession effects, with differing observed periods possibly reflecting frequency-dependent emission regions along a structured stratified jet. None the less, the short-term periodicity and exceptionally strong flares likely arise from internal jet shocks, which aligns with typical blazar behaviour. We suggest that the multiband quasi-periodicity of Ton 599 is reasonably described by a combination of geometric effects (orbital motion and precession) and stochastic processes.