Simulation of the loss-cone instability in spherical systems. II. Dominating Keplerian potential

TL;DR

This paper uses N-body simulations to confirm and extend the understanding of a newly identified gravitational loss-cone instability in spherical stellar systems, highlighting its impact on phase space diffusion and loss cone dynamics.

Contribution

It provides the first non-linear simulation confirmation of the gravitational loss-cone instability and explores its effects in systems dominated by Keplerian potential.

Findings

The instability accelerates particle diffusion in phase space.

It leads to rapid repopulation of the loss cone.

The instability saturates earlier than previously expected.

Abstract

A new so-called `gravitational loss-cone instability' in stellar systems has recently been investigated theoretically in the framework of linear perturbation theory and proved to be potentially important in understanding the physical processes in centres of galaxies, star clusters, and the Oort comet cloud. Using N-body simulations, we confirm previous findings and go beyond the linear theory. Unlike the well-known instabilities, the new one shows no notable change in spherical geometry of the cluster, but it significantly accelerates the speed of diffusion of particles in phase space leading to a repopulation of the loss cone and early instability saturation.