Detection of quasi-periodic oscillations in the 37 GHz radio light curve of the blazar Ton 599 during 1990-2020

TL;DR

This study identifies a likely quasi-periodic oscillation of approximately 2.4 years in the 37 GHz radio light curve of blazar Ton 599 over three decades, using multiple analysis methods.

Contribution

First detection of a quasi-periodic oscillation in the radio light curve of Ton 599, demonstrating the presence of periodic behavior in blazar radio emissions.

Findings

Detected a ~2.4-year QPO in Ton 599's radio data

Used Lomb-Scargle, REDFIT, and WWZ methods for analysis

Discussed potential emission models for observed QPOs

Abstract

Blazars are a subclass of radio-loud active galactic nuclei (AGNs) that display strong multi-wavelength variability on diverse timescales ranging from years down to minutes. In the last 1.5 decades, there have been occasional detections of quasi-periodic oscillations in several blazars in their time series data. We search for quasi-periodic oscillations (QPOs) in the 37 GHz radio band light curve of the flat-spectrum radio quasar Ton~599 made at the RT-22 radio telescope in Simeiz, Crimea, from 1990 to 2020. To identify and quantify the QPO nature of this radio light curve of Ton 599, we used the Lomb-Scargle periodogram (LSP), REDFIT, and weighted wavelet Z-transform (WWZ) analyses. We report the detection of a likely QPO of about 2.4 years in the 37 GHz radio light curves of Ton 599. We briefly discuss possible emission models for radio-loud active galactic nuclei that could explain such QPOs with periods of a few years.