Temporal variability and estimation of jet parameters for Ton 599

TL;DR

This study analyzes nine years of gamma-ray and radio data of blazar Ton 599, identifying four major flares, estimating jet parameters, and constraining the gamma-ray emission region based on high-energy photon detections.

Contribution

It provides a detailed temporal analysis of flaring activity, models flare profiles with exponential functions, and estimates jet physical parameters, offering new insights into the emission region location.

Findings

Four major gamma-ray flares identified over nine years.

High-energy photons (>10 GeV) detected during the fourth flare.

Emission region possibly near the outer edge of the broad line region.

Abstract

The TeV blazar Ton 599 has exhibited a peculiar flare in 2017 November. The temporal variation of the source is studied using simultaneous $\gamma$-ray data from $\textit{Fermi}$ Large Area Telescope and radio data from Owens Valley Radio Observatory's 40 m telescope, over the period of nine years. Four major flaring periods are observed in the $\gamma$-ray energy band of 0.1-300 GeV. These periods are studied on a shorter timescale and modeled with a time-dependent function containing exponential rising and decaying components. The physical parameters of the jet are estimated numerically and compared with those reported in the literature. During the fourth flare a bunch of high energy photons ($>$10 GeV) were detected. The two highest energy photons having an energy of 76.9 GeV and 61.9 GeV are detected on MJD 58059.0 and 58073.3, respectively. This observation possibly constrains the $\gamma$-ray emission region to lie near outer edge or outside the broad line region of size $\sim$0.08 pc. The variation of equivalent width of a Mg-II line is studied using the spectroscopic data from Steward observatory. It was observed that the equivalent width of the line varies inversely with the underlying power-law continuum.