Accretion-induced Collapse of Dark Matter-admixed Rotating White Dwarfs: Dynamics and Gravitational-wave Signals

TL;DR

This paper models the collapse of dark matter-admixed rotating white dwarfs, revealing unique gravitational-wave signatures that could help detect dark matter in future gravitational-wave observations.

Contribution

First simulation of gravitational waves from dark matter-admixed white dwarf collapse, showing distinctive signals for future detection.

Findings

Dark matter follows normal matter during collapse, forming a bound core.

Dark matter admixture affects gravitational-wave spectral features.

Detectable low-frequency gravitational waves can originate from dark matter collapse in our galaxy.

Abstract

We present two-dimensional hydrodynamic simulations of the accretion-induced collapse (AIC) of rotating white dwarfs admixed with an extended component of dark matter (DM) comprising of sub-GeV degenerate fermionic DM particles. We find that the DM component would follow the collapse of the normal matter (NM) component to become a bound DM core. Thus, we demonstrate how a DM-admixed neutron star could form through DM-admixed AIC (DMAIC) for the first time, with the dynamics of DM taken into account. The gravitational-wave (GW) signature from the DMAIC shows distinctive features. In the diffusive DM limit, the DM admixture indirectly suppresses the post-bounce spectral peak of the NM GWs. In the compact DM limit, the collapse dynamics of the DM in a Milky Way event generate GWs that are strong enough to be detectable by Advanced LIGO as continuous low-frequency ($< 1000$ Hz) signals after the NM core bounce. Our study not only is the first-ever computation of GW from a collapsing DM object but also provides the key features to identify DM in AIC events through future GW detections.