Gravitational-wave Emission from a Primordial Black Hole Inspiraling inside a Compact Star: a Novel Probe for Dense Matter Equation of State

TL;DR

This paper investigates gravitational wave signals from primordial black holes inspiraling into compact stars, proposing a new method to probe the dense matter equation of state using gravitational wave observations.

Contribution

It models the inspiral process for different star types and predicts detectable gravitational wave signals, highlighting potential for constraining dense matter properties.

Findings

Advanced LIGO can detect small black holes inspiraling into stars at 10 kpc.

Next-generation detectors can observe these events up to 1 Mpc for small black holes.

Distinct gravitational wave signatures can differentiate between strange stars and neutron stars.

Abstract

Primordial black holes of planetary masses captured by compact stars are widely studied to constrain their composition fraction of dark matter. Such a capture may lead to an inspiral process and be detected through gravitational wave signals. In this Letter, we study the post-capture inspiral process by considering two different kinds of compact stars, i.e., strange stars and neutron stars. The dynamical equations are numerically solved and the gravitational wave emission is calculated. It is found that the Advanced LIGO can detect the inspiraling of a $10^{-5}$ solar mass primordial black hole at a distance of 10 kpc, while a Jovian-mass case can even be detected at megaparsecs. Promisingly, the next generation gravitational wave detectors can detect the cases of $10^{-5}$ solar mass primordial black holes up to ${\sim}1$ Mpc, and can detect Jovian-mass cases at several hundred megaparsecs. Moreover, the kilohertz gravitational wave signal shows significant differences for strange stars and neutron stars, potentially making it a novel probe to the dense matter equation of state.