Accretion of dark matter by stars

TL;DR

This paper investigates how light dark matter fields, like axions, can accumulate in stars, forming stable configurations and avoiding collapse into black holes through gravitational cooling, using advanced numerical methods.

Contribution

It demonstrates the formation of stable dark matter cores in stars and explores mechanisms preventing stellar collapse, employing both perturbative and nonlinear numerical relativity techniques.

Findings

Dark matter can accumulate in stellar centers forming oscillating configurations.

These configurations are stable across most parameter ranges.

Collapse to black holes is prevented by gravitational cooling mechanisms.

Abstract

Searches for dark matter imprints are one of the most active areas of current research. We focus here on light fields with mass $m_B$, such as axions and axion-like candidates. Using perturbative techniques and full-blown nonlinear Numerical Relativity methods, we show that (i) dark matter can pile up in the center of stars, leading to configurations and geometries oscillating with frequency which is a multiple of f=$2.5 10^{14}$ $m_B c^2$/eV Hz. These configurations are stable throughout most of the parameter space, and arise out of credible mechanisms for dark-matter capture. Stars with bosonic cores may also develop in other theories with effective mass couplings, such as (massless) scalar-tensor theories. We also show that (ii) collapse of the host star to a black hole is avoided by efficient gravitational cooling mechanisms.