Limits on axion-like particles from Mrk 421 with 4.5-year period observations by ARGO-YBJ and Fermi-LAT

TL;DR

This study uses 4.5 years of ARGO-YBJ and Fermi-LAT data of Mrk 421 to search for ALP-photon oscillation effects, setting new constraints on ALP parameters without detecting a significant effect.

Contribution

First combined analysis of multi-year gamma-ray data from ARGO-YBJ and Fermi-LAT to constrain ALP-photon coupling in blazar spectra.

Findings

No significant ALP-photon oscillation detected.

Combined data improves constraints on ALP parameters.

Upper limits on ALP-photon coupling within specified mass range.

Abstract

In this work, we investigate the axion-like particle (ALP)-photon oscillation effect in the spectra of the blazar Markarian 421 (Mrk 421) using 4.5 years of the Astrophysical Radiation with Ground-based Observatory at YangBaJing (ARGO-YBJ) and Fermi Large Area Telescope (Fermi-LAT) data. These data are collected during the common operation time, which cover ten activity phases of Mrk 421. No significant ALP-photon oscillation effect is confirmed. On the other hand, not all the observations of the ten phases can be individually used to set the 95% confidence level ($\rm C.L.$) constraint on the ALP parameter space. However, the constraint can be significantly improved if the analyses for the ten phases are combined. We find that the upper limit at 95% $\rm C.L.$ on the ALP-photon coupling $g_{a\gamma}$ set by the ARGO-YBJ and Fermi-LAT observations of Mrk 421 is within $\sim [2\times 10^{-11}, \ 6\times 10^{-11}] \rm \, GeV^{-1}$ for the ALP mass of $\sim 5\times 10^{-10}$ eV $\lesssim m_a \lesssim 5\times 10^{-7}\, \rm eV$.