R-mode oscillations and rocket effect in rotating superfluid neutron stars. I. Formalism

TL;DR

This paper develops a formalism for r-mode oscillations in rotating superfluid neutron stars, introducing a new damping mechanism called the rocket effect due to particle number changing processes, within a two-fluid model.

Contribution

It presents a novel hydrodynamical formalism incorporating particle number changing processes and the rocket effect in r-mode oscillations of superfluid neutron stars.

Findings

Derived new dissipative terms related to particle number changes

Identified two types of r-mode oscillations: comoving and countermoving

Established the formalism for analyzing damping mechanisms in superfluid neutron stars

Abstract

We derive the hydrodynamical equations of r-mode oscillations in neutron stars in presence of a novel damping mechanism related to particle number changing processes. The change in the number densities of the various species leads to new dissipative terms in the equations which are responsible of the {\it rocket effect}. We employ a two-fluid model, with one fluid consisting of the charged components, while the second fluid consists of superfluid neutrons. We consider two different kind of r-mode oscillations, one associated with comoving displacements, and the second one associated with countermoving, out of phase, displacements.