Axion Clouds around Neutron Stars
Dion Noordhuis, Anirudh Prabhu, Christoph Weniger, Samuel J. Witte

TL;DR
This paper proposes that axions produced in pulsars can form dense clouds around neutron stars, leading to observable radio signatures and offering new avenues for axion detection.
Contribution
It introduces the concept of axion clouds around neutron stars formed from pulsar-produced axions, with potential observational signatures in radio spectra.
Findings
Dense axion clouds can form around neutron stars for certain axion masses.
Resonant axion-photon mixing produces detectable radio signals.
Existing telescopes could significantly improve axion-photon coupling constraints.
Abstract
Recent work has shown that axions can be efficiently produced via non-stationary pair plasma discharges in the polar cap region of pulsars. Here, we point out that for axion masses , a sizable fraction of the sourced axion population will be gravitationally confined to the neutron star. These axions accumulate over astrophysical timescales, thereby forming a dense `axion cloud' around the star. We argue that the existence of such a cloud, with densities reaching and potentially exceeding , is a generic expectation across a wide range of parameter space. For axion masses , energy is primarily radiated from the axion cloud via resonant axion-photon mixing, generating a number of distinctive signatures that include: a sharp line in the radio spectrum of…
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Taxonomy
TopicsPulsars and Gravitational Waves Research · Astrophysics and Cosmic Phenomena · Dark Matter and Cosmic Phenomena
