On the tidally induced gravitational collapse of a particle cluster

TL;DR

This paper investigates how tidal interactions in neutron star binaries can induce gravitational collapse of a particle cluster into a black hole, highlighting the effects of magnetic-type tidal forces on orbital stability.

Contribution

The study models a collisionless particle cluster around a black hole in a binary system, analyzing the influence of electric- and magnetic-type tidal fields on collapse and orbital stability.

Findings

Magnetic-type tidal forces do not significantly affect overall cluster evolution.

Some orbits are destabilized by magnetic-type tidal forces.

Stable orbits are near the companion's orbital plane and retrograde.

Abstract

An important issue in the dynamics of neutron star binaries is whether tidal interaction can cause the individual stars to collapse into black holes during inspiral. To understand this issue better, we study the dynamics of a cluster of collisionless particles orbiting a non-rotating black hole, which is part of a widely separated circular binary. The companion body's electric- and magnetic-type tidal fields distort the black hole and perturb the cluster, eventually causing the cluster to collapse into the hole as the companion spirals in under the influence of gravitational radiation reaction. We find that magnetic-type tidal forces do not significantly influence the evolution of the cluster as a whole. However, individual orbits can be strongly affected by these forces. For example, some orbits are destabilized due to the addition of magnetic-type tidal forces. We find that the most stable orbits are close to the companion's orbital plane and retrograde with respect to the companion's orbit.