First Constraint on Axion-Photon Coupling $g_{\gamma}$ from Neutron Star Observations

TL;DR

This paper introduces a new observational method using neutron star data to constrain the axion-photon coupling constant, providing the first such limit for ultra-light axions independent of the decay constant.

Contribution

It presents a novel approach to constrain axion-photon coupling directly from neutron star observations, independent of the axion decay constant.

Findings

First constraint on $g_{\gamma}$: |g_{\gamma}|<0.93 at 1σ for $m_a<10^{-11}$ eV

Utilizes data from neutron star PSR B1919+21 with FAST telescope

Method is independent of the axion decay constant $f_a$

Abstract

We propose a novel method to detect axions which uniquely depends on the dimensionless axion-photon coupling $g_{\gamma}$, independent of the suppressive axion decay constant $f_a$. Using neutron star PSR B1919+21 data from the Five-hundred-meter Aperture Spherical Telescope, we derive the first constraint $|g_{\gamma}|<0.93$ at $1\sigma$ confidence level for ultra-light axions ($m_a < 10^{-11}$ eV).