Axions may be produced thermally inside the cores of neutron stars (NSs), escape the stars due to their weak interactions with matter,
and subsequently convert into X-rays in the magnetic fields surrounding the NSs. I will describe a hard X-ray search from 2 – 8
keV for X-rays arising from this emission mechanism from the nearby Magnificent Seven isolated NSs using archival XMM-Newton and Chandra data. This search leads to the strongest limits to-date on the product of the axion-photon and axion-nucleon couplings for axion masses below ~1e−4 eV. Moreover, I will show that an observed excess
of hard X-rays from the Magnificent Seven may arise from axions. I will discuss near-term measurements and analyses to help rule out or confirm this possibility, including preliminary results from a search with NuSTAR data for axion-induced X-rays from nearby star clusters.