English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Axions may be produced thermally inside the cores of neutron stars (NSs),escape the stars due to their feeble interactions with matter, and subsequentlyconvert into X-rays in the magnetic fields surrounding the stars. We show thata recently-discovered excess of hard X-ray emission in the 2 - 8 keV energyrange from the nearby Magnificent Seven isolated NSs could be explained by thisemission mechanism. These NSs are unique in that they had previously beenexpected to only produce observable flux in the UV and soft X-ray bands fromthermal surface emission at temperatures ~100 eV. No conventional astrophysicalexplanation of the Magnificent Seven hard X-ray excess exists at present. Weshow that the hard X-ray excess may be consistently explained by an axion-likeparticle with mass $m_a \lesssim 2 \times 10^{-5}$ eV and $g_{a\gamma\gamma}\times g_{ann} \in (2 \times 10^{-21}, 10^{-18})$ GeV$^{-1}$ at 95\%confidence, accounting for both statistical and theoretical uncertainties,where $g_{a\gamma\gamma}$ ($g_{ann}$) is the axion-photon (axion-neutron)coupling constant.

Axion Emission Can Explain a New Hard $X$-ray Excess from Nearby Isolated Neutron Stars