Gravitational synchronization in bosonic dark matter admixed neutron stars

TL;DR

This paper investigates how ultralight bosonic dark matter interacts with neutron stars, revealing gravitationally synchronized oscillation modes that could impact gravitational-wave signals and neutron-star physics.

Contribution

It introduces a numerical relativity model of fermion-boson stars showing gravitational synchronization of oscillation modes, a novel phenomenon in dark matter-neutron star interactions.

Findings

Discovery of gravitational synchronization of oscillation modes

Identification of new multi-state scalar configurations

Potential implications for gravitational-wave detection

Abstract

While the search for dark matter remains a central focus of modern astrophysics and high-energy physics, neutron stars provide natural laboratories in which the interaction between dark matter and baryonic matter can be studied. In this work we model dark matter as an ultralight bosonic field, which can accrete onto the neutron star and form a composite object bound through gravity. Using long-term, numerical relativity simulations in spherical symmetry, we extract and analyze the frequency spectra of the radial oscillation modes of fermion-boson stars. Our simulations reveal that the fermionic and bosonic components synchronize through gravitational coupling, enriching their oscillation spectrum. This synchronization leads to new multi-state scalar configurations and reshapes the hierarchy of the neutron-star radial modes. We further propose a procedure to compute the values of the new dominant modes as a function of the bosonic mass, and discuss the implications for neutron-star physics and gravitational-wave astronomy.