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

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 postcapture 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 next generation gravitational wave detectors can detect the inspiraling of a 10 −5 M primordial black hole at a distance of 1 kpc. A Jovianmass case can even be detected at 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.