Proto-neutron Stars with Dark Matter Admixture: A Single-Fluid Approach

TL;DR

This study explores how dark matter influences proto-neutron stars' evolution and structure using a single-fluid model, revealing impacts on thermal energy, neutrino emission, and setting constraints on dark matter mass.

Contribution

It introduces a single-fluid approach to model dark matter effects in proto-neutron stars, analyzing thermal and structural impacts during evolution.

Findings

Dark matter absorbs thermal energy, affecting neutrino emission.

Neutrinos significantly support pressure, limiting dark matter accretion.

Upper dark matter mass limit of 0.62 GeV for proto-neutron stars.

Abstract

This work investigates the impact of dark matter (DM) on the microscopic and macroscopic properties of proto-neutron stars (PNSs). We employ a single-fluid framework in which DM interacts with ordinary matter (OM) via the Higgs portal and remains in thermal equilibrium through non-gravitational interactions. Using a quasi-static approximation, we analyze the evolution of PNSs during the Kelvin-Helmholtz phase by varying the DM mass while keeping the entropy per baryon and lepton fraction fixed. Our results show that DM absorbs thermal energy from the stellar medium without efficient re-emission, thereby altering neutrino emission and affecting the star's thermal evolution history. Furthermore, neutrinos contribute significantly to pressure support in the PNS phase, inhibiting DM mass accretion during neutrino-trapped stages. Based on the requirement to satisfy the observed $2,\rm M_\odot$ neutron star mass constraint and to maintain consistency with supernova remnant data, we suggest an upper limit of $m_\chi \leq 0.62,\rm GeV$ for the DM mass that can accrete in evolving PNSs, within the model framework. In contrast, we established that cold neutron stars (NSs) can support higher DM masses without compromising equilibrium stability, owing to increased central density, enhanced gravitational binding energy, and reduced thermal pressure.