X-ray Searches for Axions from Super Star Clusters

TL;DR

This study searches for axions emitted by super star clusters using X-ray data, constraining the axion-photon coupling strength but finding no evidence of axions.

Contribution

It introduces a novel method of using Galactic magnetic field models and archival X-ray data to search for axions from specific stellar clusters.

Findings

No significant axion signal detected

Constraints on axion-photon coupling strength

Limits set for axion masses below 5×10^{-11} eV

Abstract

Axions may be produced in abundance inside stellar cores and then convert into observable X-rays in the Galactic magnetic fields. We focus on the Quintuplet and Westerlund 1 super star clusters, which host large numbers of hot, young stars including Wolf-Rayet stars; these stars produce axions efficiently through the axion-photon coupling. We use Galactic magnetic field models to calculate the expected X-ray flux locally from axions emitted from these clusters. We then combine the axion model predictions with archival Nuclear Spectroscopic Telescope Array (NuSTAR) data from 10 - 80 keV to search for evidence of axions. We find no significant evidence for axions and constrain the axion-photon coupling $g_{a\gamma\gamma} \lesssim 3.6 \times 10^{-12}$ GeV$^{-1}$ for masses $m_a \lesssim 5 \times 10^{-11}$ eV at 95\% confidence.