Implications of the r-mode instability of rotating relativistic stars

TL;DR

This paper reviews how the r-mode instability in rotating relativistic stars, especially neutron stars, could limit their spin and produce gravitational waves detectable by advanced observatories like LIGO II.

Contribution

It provides a comprehensive review of recent developments, highlighting the potential observability of gravitational waves from r-mode instabilities and discussing the effects of dissipative mechanisms.

Findings

R-mode instability likely limits neutron star spin rates.

Gravitational waves from these instabilities may be detectable by LIGO II.

Dissipative mechanisms influence the growth and saturation of the instability.

Abstract

Several recent surprises appear dramatically to have improved the likelihood that the spin of rapidly rotating, newly formed neutron stars (and, possibly, of old stars spun up by accretion) is limited by a nonaxisymmetric instability driven by gravitational waves. Except for the earliest part of the spin-down, the axial l=m=2 mode (an r-mode) dominates the instability, and the emitted waves may be observable by detectors with the sensitivity of LIGO II. A review of these hopeful results is followed by a discussion of constraints on the instability set by dissipative mechanisms, including viscosity, nonlinear saturation, and energy loss to a magnetic field driven by differential rotation.