Axial Oscillations of Viscous Neutron Stars

TL;DR

This paper investigates the oscillation modes of viscous neutron stars using a new relativistic hydrodynamics framework, revealing viscosity-driven modes and long-lived oscillations with potential astrophysical significance.

Contribution

It introduces a well-posed, causal relativistic hydrodynamics approach to study neutron star oscillations, uncovering new viscosity-driven mode families and mode avoidance phenomena.

Findings

Discovered viscosity-driven families of oscillation modes.

Identified long-lived modes with potential astrophysical relevance.

Observed mode avoidance in certain mode families.

Abstract

The oscillation modes of stars play an important role in observations, and on the understanding of stellar stability properties. The role of viscosity in the oscillation modes of compact stars has been so far understood very loosely only, in absence of a well posed framework. We use recent breakthroughs in the formulation of a causal and stable theory of relativistic hydrodynamics, to study oscillation modes of neutron stars. We characterize the axial spectrum of compact stars and uncover new, viscosity-driven families of modes, without a perfect fluid counterpart. Our results show mode avoidance in some of these families, and a spectrum of long-lived modes, whose role in astrophysical, dynamical processes is yet to be understood.