Astroparticle physics with compact objects

TL;DR

This paper reviews how compact objects like neutron stars and white dwarfs are used in astroparticle physics to search for hypothetical particles such as dark matter and axions, providing observational constraints and potential signatures.

Contribution

It summarizes recent methods and results in using compact objects to detect or constrain properties of dark matter and axions, highlighting astrophysical limits and observational signatures.

Findings

Dark matter can accumulate in compact objects, affecting their thermal evolution.

Observations of neutron stars and white dwarfs set upper limits on axion properties.

Astrophysical processes in compact objects can reveal or constrain new physics beyond the Standard Model.

Abstract

Probing the existence of hypothetical particles beyond the Standard model often deals with extreme parameters: large energies, tiny cross-sections, large time scales, etc. Sometimes laboratory experiments can test required regions of parameter space, but more often natural limitations leads to poorly restrictive upper limits. In such cases astrophysical studies can help to expand the range of values significantly. Among astronomical sources, used in interests of fundamental physics, compact objects -- neutron stars and white dwarfs, -- play a leading role. We review several aspects of astroparticle physics studies related to observations and properties of these celestial bodies. Dark matter particles can be collected inside compact objects resulting in additional heating or collapse. We summarize regimes and rates of particle capturing as well as possible astrophysical consequences. Then we focus on a particular type of hypothetical particles -- axions. Their existence can be uncovered due to observations of emission originated due to Primakoff process in magnetospheres of neutron stars or white dwarfs. Alternatively, they can contribute to cooling of these compact objects. We present results in these areas, including upper limits based on recent observations.