From Capture to Collapse: Revisiting Black Hole formation by Fermionic Asymmetric Dark Matter in Neutron Stars

TL;DR

This paper reevaluates constraints on fermionic asymmetric dark matter in neutron stars, showing that previous limits can be significantly relaxed when more accurate physical processes are considered, impacting dark matter detection prospects.

Contribution

It provides a refined analysis of dark matter capture and collapse in neutron stars, improving upon previous models by including detailed physical effects and challenging earlier constraints.

Findings

Previous limits on dark matter properties can be relaxed by orders of magnitude.

Improved modeling of capture, thermalization, and collapse processes alters constraints.

Certain dark matter parameter spaces are less constrained than previously thought.

Abstract

Fermionic asymmetric dark matter (ADM) can be captured in neutron stars (NSs) via scatterings with the star constituents. The absence of dark matter annihilation due to its asymmetric nature leads to ADM accumulation in the NS core, potentially reaching densities sufficient to exceed the Chandrasekhar limit and trigger its gravitational collapse into a black hole (BH), eventually consuming the NS from within. Therefore, the existence and observation of old neutron stars provide a means to constrain the properties of ADM. We revisit previous constraints on the mass and scattering cross section off neutrons of fermionic ADM across a class of models. We critically examine common simplifying approximations used in the literature to derive these limits. Our analysis includes improved treatments of dark matter capture, thermalization, BH formation, accretion, and evaporation. We find that previous results can be relaxed by a few orders of magnitude once these effects are properly accounted for.