Constraint on hybrid stars with gravitational wave events

TL;DR

This paper explores the potential of identifying dark matter hybrid stars in gravitational wave data, analyzing their stability and implications for dark matter models based on recent LIGO/Virgo observations.

Contribution

It extends the analysis of LIGO/Virgo gravitational wave events to include hybrid stars composed of dark matter and nuclear matter, focusing on their stability constraints.

Findings

Hybrid stars could explain some gravitational wave signals.

Saddle instability constrains dark matter models.

Hybrid stars may be the lightest black holes or heaviest neutron stars.

Abstract

Motivated by the recent discoveries of compact objects from LIGO/Virgo observations, we study the possibility of identifying some of these objects as compact stars made of dark matter called dark stars, or the mix of dark and nuclear matters called hybrid stars. In particular, in GW190814, a new compact object with 2.6 $M_{\odot}$ is reported. This could be the lightest black hole, the heaviest neutron star, and a dark or hybrid star. In this work, we extend the discussion on the interpretations of the recent LIGO/Virgo events as hybrid stars made of various self-interacting dark matter (SIDM) in the isotropic limit. We pay particular attention to the saddle instability of the hybrid stars which will constrain the possible SIDM models.