Viscous damping of r-modes and emission of gravitational waves

TL;DR

This paper investigates how viscous damping affects r-mode oscillations in neutron stars and estimates the resulting gravitational wave emission, considering different equations of state and neutron star parameters.

Contribution

It provides a detailed analysis of viscous damping effects on r-modes, incorporating realistic equations of state and boundary layer physics to predict gravitational wave signals.

Findings

Viscous damping significantly influences r-mode stability.

Critical frequencies depend on neutron star mass and equation of state.

Estimated gravitational wave strain amplitudes for various pulsar models.

Abstract

The Rossby mode (r-mode) perturbation in pulsars as a steady gravitational wave (GW) source has been explored. The effect of a rigid crust on viscous damping and dissipation rate in the boundary layer between fluid core and crust has been studied. The intensity of the emitted GWs in terms of the strain tensor amplitude has been estimated with the approximation of slow rotation using equation of state derived from the APR and Skyrme effective interactions with Brussels-Montreal parameter sets. The core of the neutron star has been considered to be $\beta$-equilibrated nuclear matter containing neutrons, protons, electrons and muons, surrounded by a solid crust. Calculations have been made for critical frequencies, the time evolution and the rate of change of the spin frequencies across a broad spectrum of pulsar masses.