Constraints on the fermionic dark matter from observations of neutron stars

TL;DR

This paper investigates how asymmetric fermionic dark matter influences neutron star properties, deriving new constraints on dark matter mass and fraction based on astrophysical and gravitational wave observations.

Contribution

It introduces a novel analysis of dark matter effects on neutron star structure and derives upper limits on dark matter content using recent observational data.

Findings

Dark matter core decreases neutron star mass and deformability.

Dark matter halo increases mass and deformability.

Extended halos are incompatible with GW170817 constraints.

Abstract

We study an impact of asymmetric fermionic dark matter on neutron star properties, including tidal deformability, mass, radius, etc. We present the conditions at which dark matter particles tend to form a compact structure in a core of the star or create an extended halo around it. We show that compact core of dark matter leads to a decrease of the total gravitational mass and tidal deformability compared to a pure baryonic star, while presence of a dark matter halo increases those observable quantities. By imposing an existing astrophysical and gravitational wave constraints set by LIGO/Virgo Collaboration together with the recent results on the spatial distribution of dark matter in the Milky Way we determine a new upper limit on the mass and fraction of dark matter particles inside compact stars. Furthermore, we show that the formation of an extended halo around a NS is incompatible with the GW170817 tidal deformability constraint.