Comment on "Instabilities in Close Neutron Star Binaries"

TL;DR

This paper critiques recent numerical calculations of neutron star binaries, highlighting that their configurations may not lead to black hole formation due to excessive angular momentum and mass.

Contribution

It points out a potential flaw in previous neutron star binary models, emphasizing the importance of angular momentum constraints for black hole formation.

Findings

Calculated configurations have J > M^2, exceeding Kerr black hole limits

Previous models suggested stable orbits with different angular momentum properties

Highlights the need to reconsider stability criteria in strong-field gravity simulations

Abstract

In a recent Physical Review Letter, Wilson and Mathews presented some interesting numerical calculations of a system of two equally massive neutron stars in strong-field gravity. In particular they estimated the innermost stable circular orbit in their system. Here we point out a possibly important consequence of their results: Their calculated configurations have total angular momentum $J$ and total mass $M$ too large to form any Kerr black hole: $J>M^2$, in constrast to previous calculations of the innermost stable circular orbit.