Possible nature of Dark Matter

TL;DR

This study explores how dark matter, assumed to be self-interacting and particle-like, affects neutron star models, analyzing various compositions and constraints to understand its distribution and properties within stars.

Contribution

It introduces models of neutron stars with significant dark matter content, considering both fermionic and bosonic particles, and examines their impact on star structure and observable properties.

Findings

Fermionic dark matter is distributed throughout the neutron star, not just in the core.

Dark matter can constitute up to 15% of the neutron star's mass.

Models are consistent with observational constraints on mass, radius, and tidal deformability.

Abstract

{We present a study of neutron star models that contain dark matter (DM) in the core. The DM is assumed to have a particle nature and to be self-interacting. Using constraints on the mass and radius of neutron stars, we investigate the allowed properties of either bosonic or fermionic DM particles. We consider cases where it constitutes up to 15\% of the mass of the star, even though conventional mechanisms cannot generate such large fractions. For this purpose three different models of neutron stars are considered, the first involving nucleons only, the second including hyperons, and the last involving strange matter in the core. Different EoSs are constructed for the various cases of fermionic and bosonic DM. These EoSs are solved for selected properties of the DM particles and the results are tested against mass, radius and tidal deformability constraints for neutron stars. The distribution of energy density of DM and ordinary matter inside the neutron stars is also presented. It is found that if the DM is fermionic in nature it does not just sit in the core but it is present everywhere in the star, from the centre to outside the surface and may even envelop it.