Axion Production in Pulsar Magnetosphere Gaps

TL;DR

This paper proposes that pulsar magnetosphere gaps produce axions with energies linked to gap oscillations, potentially detectable through radio signals, offering a new method to probe axion-photon couplings beyond current bounds.

Contribution

It introduces a novel mechanism for axion production in pulsar gaps and suggests observational strategies to detect these axions via radio telescopes.

Findings

Axions produced in pulsar gaps can exceed ambient dark matter density.

A fraction of axions may convert to photons, producing detectable radio signals.

Observations with FAST and SKA can test axion-photon couplings below current limits.

Abstract

Pulsar magnetospheres admit non-stationary vacuum gaps that are characterized by non-vanishing ${\bf{E}} \cdot {\bf{B}}$. The vacuum gaps play an important role in plasma production and electromagnetic wave emission. We show that these gaps generate axions whose energy is set by the gap oscillation frequency. The density of axions produced in a gap can be several orders of magnitude greater than the ambient dark matter density. In the strong pulsar magnetic field, a fraction of these axions may convert to photons, giving rise to broadband radio signals. We show that dedicated observations of nearby pulsars with radio telescopes (FAST) and interferometers (SKA) can probe axion-photon couplings that are a few orders of magnitude lower than current astrophysical bounds.