Mergers of Magnetized Neutron Stars with Spinning Black Holes: Disruption, Accretion and Fallback

TL;DR

This study models the merger of a magnetized neutron star with a spinning black hole, analyzing gravitational waves and fallback accretion, and finds minimal impact from magnetization on the disruption process.

Contribution

It provides the first detailed general relativity simulation of a magnetized neutron star merging with a spinning black hole, including fallback and accretion analysis.

Findings

Negligible effects from initial magnetization on disruption

Most neutron star material falls back within 10 seconds

Nearly all material interacts with the central engine within 3 hours

Abstract

We investigate the merger of a neutron star (of compaction ratio $0.1$) in orbit about a spinning black hole in full general relativity with a mass ratio of $5:1$, allowing for the star to have an initial magnetization of $10^{12} {\rm Gauss}$. We present the resulting gravitational waveform and analyze the fallback accretion as the star is disrupted. The evolutions suggest no significant effects from the initial magnetization. We find that only a negligible amount of matter becomes unbound; $99%$ of the neutron star material has a fallback time of 10 seconds or shorter to reach the region of the central engine and that $99.99%$ of the star will interact with the central disk and black hole within 3 hours.