Transient Radio Signatures from Neutron Star Encounters with QCD Axion Miniclusters

TL;DR

This paper predicts that dense axion miniclusters interacting with neutron stars produce transient radio signals, which could be detected by current telescopes, offering a new way to discover QCD axion dark matter.

Contribution

It quantifies the properties and encounter rates of axion miniclusters with neutron stars, highlighting their potential as observable signals for axion dark matter detection.

Findings

Encounter rates of 1-100 per day for axion miniclusters with neutron stars.

Transient radio signals last from one day to a few months.

Signals are concentrated towards the Galactic center and are detectable with current telescopes.

Abstract

The QCD axion is expected to form dense structures known as axion miniclusters if the Peccei-Quinn symmetry is broken after inflation. Miniclusters that have survived until today will interact with neutron stars (NSs) in the Milky Way to produce transient radio signals from axion-photon conversion in the NS magnetosphere. We quantify the properties of these encounters and find that they occur frequently ($\mathcal{O}(1-100)\,\mathrm{day}^{-1}$); last between a day and a few months; are spatially clustered towards the Galactic center; and can reach observable fluxes. These radio transients are within reach of current generation telescopes and therefore offer a promising pathway to discovering QCD axion dark matter.