Non-radial Oscillation Modes of Compact Stars with a Crust

TL;DR

This study investigates how the presence of a crust affects the high-frequency non-radial oscillation modes of neutron stars and strange quark stars, revealing significant differences in mode frequencies due to crust composition.

Contribution

It introduces a two-component model for compact stars and analyzes the impact of different crust types on their oscillation modes using relativistic Cowling approximation.

Findings

Crust increases p-mode frequency in neutron stars slightly.

Strangelet crust significantly raises the f-mode frequency in strange stars.

Crust composition has a notable effect on oscillation mode frequencies.

Abstract

Oscillation modes of isolated compact stars can, in principle, be a fingerprint of the equation of state (EoS) of dense matter. We study the non-radial high-frequency l=2 spheroidal modes of neutron stars and strange quark stars, adopting a two-component model (core and crust) for these two types of stars. Using perturbed fluid equations in the relativistic Cowling approximation, we explore the effect of a strangelet or hadronic crust on the oscillation modes of strange stars. The results differ from the case of neutron stars with a crust. In comparison to fluid-only configurations, we find that a solid crust on top of a neutron star increases the p-mode frequency slightly with little effect on the f-mode frequency, whereas for strange stars, a strangelet crust on top of a quark core significantly increases the f-mode frequency with little effect on the p-mode frequency.