X-Ray Searches for Axions from Super Star Clusters
Christopher Dessert, Joshua W. Foster, Benjamin R. Safdi
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 ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}\ensuremath{\lesssim}3.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$ for masses ${m}_{a}\ensuremath{\lesssim}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\text{ }\text{ }\mathrm{eV}$ at 95% confidence.