Towards real neutron star seismology: Accounting for elasticity and superfluidity

TL;DR

This paper investigates how elasticity and superfluidity in neutron star crusts influence their oscillation spectra, revealing significant effects of superfluid neutrons and effective mass on star vibrations.

Contribution

It introduces a detailed model accounting for elasticity, superfluidity, and composition stratification in neutron star oscillations, advancing the understanding of their seismic behavior.

Findings

Superfluid neutrons and their effective mass significantly impact oscillation modes.

Elasticity and entrainment alter the star's shear and acoustic mode spectra.

The model provides a framework for interpreting neutron star seismology data.

Abstract

We study the effects of an elastic crust on the oscillation spectrum of superfluid neutron stars. Within the two fluid formalism, we consider Newtonian stellar models that include the relevant constituents of a mature neutron stars. The core is formed by a mixture of superfluid neutrons and a conglomerate of charged particles, while the inner crust is described by a lattice of nuclei permeated by superfluid neutrons. We linearise the Poisson and the conservation equations of nonrotating superfluid stars and study the effects of elasticity, entrainment and composition stratification on the shear and acoustic modes. In both the core and the crust, the entrainment is derived from recent results for the nucleon effective mass. Solving the perturbation equations as an eigenvalue problem, we find that the presence of superfluid neutrons in the crust and their large effective mass may have significant impact on the star's oscillation spectrum.