Fate of a neutron star with an endoparasitic black hole and implications for dark matter

Abstract

We study the dynamics and observational signatures of a neutron star being consumed by a much less massive black hole residing inside the star. This phenomenon could arise in a variety of scenarios, including after the capture of a primordial black hole, or in some models of asymmetric dark matter where the dark matter particles collect at the center of a neutron star and eventually collapse to form a black hole. However, the details of how the neutron star implodes are not well known, which is crucial to determining the observational implications of such events. We utilize fully general relativistic simulations to follow the evolution of such a black hole as it grows by several orders of magnitude, and ultimately consumes the neutron star. We consider a range of spin values for the neutron star, from non-rotating stars, to those with millisecond periods, as well as different equations of state. We find that as the black hole grows, it obtains a non-negligible spin and induces differential rotation in the core of the neutron star. In contrast to previous studies, we find that the amount of dynamical ejecta is very small, even for rapidly rotating stars, dampening the prospects for producing a kilonova-type electromagnetic signal from such events. We comment on other possible electromagnetic and gravitational signals.arXiv:1909.07968v1 [gr-qc]

Coalescence of black hole–neutron star binaries

“…We note that, while the physical reason of the behavior at very low-mass ratios described above is not fully understood yet, it may not be unexpected taking the fact that an extremely low-mass black hole with M BH ( M NS ðQ ( 1Þ cannot make the neutron star unbound because of the tiny contribution of such a minute black hole to the dynamics of the entire system. Related simulations have been performed in the context of consumption of a neutron star by an endoparasitic black hole at the center (East and Lehner 2019;Richards et al 2021).…”

Distinguishing double neutron star from neutron star-black hole binary populations with gravitational wave observations

“…Moreover, we are focusing on black hole masses up to 2 M ⊙ . These may involve BHs of primordial origin or dark matter cores (see Appendix A), and theoretical calculation in these scenarios suggest that BH spins should be negligible [119,121,122].…”

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

“…Interestingly, during such a collision, the PBH-compact star system will also emit gravitational waves (GWs) as the PBH accretes matter from the compact star. Kurita & Nakano (2016) and East & Lehner (2019) studied the GW signals from an accreting PBH, which is assumed to have plunged into its compact companion and stays at the exact center of the neutron star (NS). Horowitz & Reddy (2019) and Génolini et al (2020) studied the GW emission during the inspiraling process of a PBH inside a NS, but their treatment of the dynamics and the compact star structure is still preliminary.…”