Fermionic versus Bosonic Dark Matter in Neutron Stars: A Bayesian Study with Multi-Density Constraints

TL;DR

This study uses Bayesian analysis to compare fermionic and bosonic dark matter models in neutron stars, incorporating multiple constraints and finding that current data cannot distinguish between these dark matter types.

Contribution

It introduces a comprehensive Bayesian framework to constrain dark matter properties in neutron stars, considering multiple models and observational data.

Findings

Dark matter fraction in neutron stars is constrained to be under 10%.

Dark matter presence slightly reduces neutron star mass, radius, and deformability.

No statistical preference found among fermionic and bosonic dark matter models.

Abstract

We perform a comparative Bayesian analysis of fermionic and bosonic dark matter admixed neutron stars (DMANS) by incorporating a comprehensive set of theoretical, experimental, and astrophysical constraints. The hadronic matter equation of state (EoS) is modeled using a relativistic mean-field approach, constrained by chiral effective field theory ($\chi$EFT) calculations at low densities, finite nuclei and heavy-ion collision data at intermediate densities, and neutron star (NS) observations at high densities. For the dark sector, we consider fermionic dark matter (FDM) interacting via a dark vector meson, and two bosonic dark matter models (BDM1 and BDM2) characterized by self-interacting scalar fields. Bayesian inference is employed to constrain the model parameters, including the dark matter mass, coupling strength, and dark matter fraction within NSs. Our analysis finds that all models yield consistent nuclear matter parameters, allowing a small dark matter fraction under 10%. The presence of dark matter slightly softens the EoS, leading to a modest reduction in NS mass, radius, and tidal deformability, though all models remain compatible with NICER and GW170817 observations. The log-evidence and likelihood analyses reveal no statistical preference among the FDM and BDM models, indicating that current astrophysical data cannot decisively distinguish between fermionic and bosonic dark matter scenarios. This study provides a unified statistical framework to constrain dark matter properties using NS observables.