Constraining axion by polarized prompt emission from gamma ray bursts

TL;DR

This paper proposes a method to constrain the existence of invisible axions by analyzing the polarization of gamma-ray bursts, using the effect of axion-induced dichroism on gamma-ray polarization across energy bands.

Contribution

It introduces a novel astrophysical approach to constrain axion-photon coupling using polarized gamma-ray burst observations, providing competitive limits on axion parameters.

Findings

Derived a new constraint on axion-photon coupling: g_{aγγ} ≤ 2.2×10^{-11} GeV^{-1} for m_a=10^{-3} eV.

Constraint is competitive with laboratory experiments like CAST and improves for lower axion masses.

Utilized observed polarized gamma-ray emissions from GRBs to set bounds on axion properties.

Abstract

A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of invisible axion. The axionic induced dichroism of gamma rays at different energies should cause a misalignment of the polarization plane for higher energy events relative to that one for lower energies events resulting in the loss of statistics needed to form a pattern of the polarization signal to be recognized in a detector. According to this, any evidence of polarized gamma rays coming from an object with extended magnetic field could be interpreted as a constraint on the existence of the invisible axion for a certain parameter range. Based on reports of polarized MeV emission detected in several GRBs we derive a constraint on the axion-photon coupling. This constraint $\g_{a\gamma\gamma}\le 2.2\cdot 10^{-11} {\rm GeV^{-1}}$ calculated for the axion mass $m_a=10^{-3} {\rm eV}$ is competitive with the sensitivity of CAST and becomes even stronger for lower masses.