$\gamma$-ray Flux and Spectral Variability of Blazar Ton 599 during Its 2021 Flare

TL;DR

This study analyzes the gamma-ray flux and spectral variability of blazar Ton 599 during its 2021 flare, revealing significant flux changes, spectral modeling with a log-parabola, and insights into the emission region location.

Contribution

It provides the first detailed gamma-ray variability analysis of Ton 599 during a flare, including flux states, spectral modeling, and emission region estimation.

Findings

Maximum gamma-ray flux of 2.24e-6 ph cm^-2 s^-1 during flare

Largest flux variation (~35%) observed in main-flare epoch

Gamma-ray spectra well described by log-parabola model

Abstract

Blazars are known to emit exceptionally variable non-thermal emission over the wide range (from radio to $\gamma$-rays) of electromagnetic spectrum. We present here the results of our $\gamma$-ray flux and spectral variability study of the blazar Ton 599, which has been recently observed in the $\gamma$-ray flaring state. Using 0.1$-$300 GeV $\gamma$-ray data from the $\it{Fermi}$ Gamma-ray Space Telescope (hereinafter $\it{Fermi}$), we generated one-day binned light curve of Ton 599 for a period of about one-year from MJD 59,093 to MJD 59,457. During this one year period, the maximum $\gamma$-ray flux detected was 2.24 $\pm$ 0.25 $\times$ $10^{-6}$ ph cm$^{-2}$ s$^{-1}$ at MJD 59,399.50. We identified three different flux states, namely, epoch A (quiescent), epoch B (pre-flare) and epoch C (main-flare). For each epoch, we calculated the $\gamma$-ray flux variability amplitude (F$_{var}$) and found that the source showed largest flux variations in epoch C with F$_{var} \sim$ 35%. We modelled the $\gamma$-ray spectra for each epoch and found that the Log-parabola model adequately describes the $\gamma$-ray spectra for all the three epochs. We estimated the size of the $\gamma$-ray emitting region as 1.03 $\times$ $10^{16}$ cm and determined that the origin of $\gamma$-ray radiation, during the main-flare, could be outside of the broad line region.