Constraints on Axion-Photon Mixing from Fast Radio Burst Dispersion Measures

TL;DR

This study uses fast radio burst dispersion measures to constrain axion properties and their potential influence on photon propagation, providing new bounds on axion mass and coupling with implications for dark matter research.

Contribution

It introduces a novel method to constrain axion parameters using FRB data and Bayesian analysis, accounting for cosmological uncertainties and environmental effects.

Findings

Constraints on axion mass around 1.16 μeV

Upper limit on axion-photon coupling of 1.76×10^{-16} GeV^{-1}

Consistent results across different cosmological models

Abstract

Fast radio bursts (FRBs) offer a powerful probe of the ionized Universe through their dispersion measures (DM). While a significant fraction of the DM arises from the intergalactic medium (IGM), the contributions from the host galaxy and the immediate environment of the source remain uncertain, and the physical origin of FRBs is still under active investigation. In this work, we investigated the possibility that FRBs originate from high-magnetic-field neutron stars (NS), whose magnetospheres can facilitate axion-photon mixing. Such mixing can modify photon propagation and induce an effective contribution to the observed dispersion. Using a sample of localized FRBs with measured redshifts, we perform a Bayesian Markov Chain Monte Carlo (MCMC) analysis to constrain the axion mass $m_a$ and axion-photon coupling $g_{a\gamma\gamma}$. Within a parametric cosmological framework, we obtain $m_a = 1.16^{+4.40}_{-1.08}\,\mu{\rm eV}$ and $g_{a\gamma\gamma} = (1.76^{+6.69}_{-1.64})\times10^{-16}\,{\rm GeV}^{-1}$, together with a physically consistent intergalactic baryon fraction $f_{\rm IGM} = 0.837^{+0.053}_{-0.056}$. We further tested the robustness of our bounds against cosmological modeling assumptions by employing a non-parametric Gaussian Process reconstruction (GPR) of the DM-$z$ relation, which gives statistically consistent results.