  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.
