X-ray Search for Axions from Nearby Isolated Neutron Stars. (arXiv:1910.04164v1 [hep-ph])
<a href="http://arxiv.org/find/hep-ph/1/au:+Buschmann_M/0/1/0/all/0/1">Malte Buschmann</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Co_R/0/1/0/all/0/1">Raymond T. Co</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Dessert_C/0/1/0/all/0/1">Christopher Dessert</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Safdi_B/0/1/0/all/0/1">Benjamin R. Safdi</a>

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. We perform a
hard X-ray search from 2 – 8 keV arising from this emission mechanism from the
nearby Magnificent Seven isolated NSs using archival XMM-Newton and Chandra
data. These NSs are unique in that they have only been detected in the UV and
soft X-ray bands; their observed fluxes are thought to arise from thermal
emission at temperatures ~100 eV from the NS surfaces. We use the X-ray
datasets to set the strongest limits to-date on the product of the axion-photon
and axion-nucleon couplings for axion masses below ~$10^{-4}$ eV. Moreover, we
interpret an observed excess of hard X-rays from the Magnificent Seven in the
context of the axion model, and we discuss possible future measurements to help
rule out or confirm this possibility.

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. We perform a
hard X-ray search from 2 – 8 keV arising from this emission mechanism from the
nearby Magnificent Seven isolated NSs using archival XMM-Newton and Chandra
data. These NSs are unique in that they have only been detected in the UV and
soft X-ray bands; their observed fluxes are thought to arise from thermal
emission at temperatures ~100 eV from the NS surfaces. We use the X-ray
datasets to set the strongest limits to-date on the product of the axion-photon
and axion-nucleon couplings for axion masses below ~$10^{-4}$ eV. Moreover, we
interpret an observed excess of hard X-rays from the Magnificent Seven in the
context of the axion model, and we discuss possible future measurements to help
rule out or confirm this possibility.

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