Exploring Axion-Like Particle from observation of FSRQ Ton 599 by Fermi-LAT

TL;DR

This paper investigates how axion-like particles could influence gamma-ray spectra from the quasar Ton 599, using Fermi-LAT data to set constraints on ALP properties through photon-ALP oscillation effects.

Contribution

It provides new observational constraints on ALP parameters by analyzing gamma-ray spectra of Ton 599, considering astrophysical magnetic fields and photon oscillation effects.

Findings

Constraints on ALP-photon coupling reach about 2×10⁻¹² GeV⁻¹.

ALP mass around 10⁹ eV is constrained at 95% confidence level.

Photon-ALP oscillations can modify gamma-ray spectra in astrophysical sources.

Abstract

High energy photons traveling through astrophysical magnetic fields have the potential to undergo oscillations with axion-like particles (ALPs), resulting in modifications to the observed photon spectrum. High energy $\gamma-$ray sources with significant magnetic field strengths provide an ideal setting to investigate this phenomenon. Ton 599, a flat spectrum radio quasar with a magnetic field strength on the order of Gauss in its emission region, presents a promising opportunity for studying ALP-photon oscillations. In this study, we analyze the effects of ALP-photon oscillations on the $\gamma$-ray spectrum of Ton 599 as observed by Fermi-LAT. Our investigation considers the potential influences of the broad-line region and dusty torus on the $\gamma-$ray spectrum of Ton 599. We set the constraints on the ALP parameters at the $95\%$ confidence level, and find that the constraints on \(g_{a\gamma}\) can reach approximately \(2 \times 10^{-12}~\mathrm{GeV}^{-1}\) for \(m_a \sim 10^{9}~\mathrm{eV}\).