Universality in spacetime $\omega$ modes of quarkyonic stars

TL;DR

This paper investigates the gravitational wave $$ modes of quarkyonic stars, revealing unique signatures and universal relations that distinguish them from other compact star models, within a relativistic framework.

Contribution

It introduces a detailed model of quarkyonic matter in neutron stars and analyzes their $$ mode spectrum, highlighting distinctive features and universal relations.

Findings

Quarkyonic matter significantly alters $$ mode frequencies and damping times.

The $$ mode spectrum shows a unique signature for quarkyonic stars.

Universal relations for $$ mode frequencies are largely EOS-independent.

Abstract

The gravitational wave $\omega$ mode spectrum presents a unique window into the dense interior of neutron stars, probing physics inaccessible to electromagnetic observations. This work investigates the $\omega$ modes of compact stars composed of quarkyonic matter. The quarkyonic model, which describes a cross-over transition between nucleonic and quark matter treated as quasi-particles, is formulated within the Relativistic Mean-Field (RMF) theory using the G3 and IOPB-I parameterizations. This core is surrounded by a mantle of hadronic matter, creating a multicomponent stellar interior. The overall Equation of State (EOS) is governed by two key parameters: the transition density ($n_t$), the QCD confinement scale ($\Lambda_{\rm cs}$), which are varied to construct models consistent with current astrophysical constraints on mass and radius. We compute the complex eigenfrequencies (damped oscillations) of the fundamental and first excited $\omega$ modes using the phase-amplitude method within a full general relativistic framework. Our simulations reveal that the admixed quarkyonic structure produces a unique $\omega$ mode signature, distinctly different from pure hadronic or hybrid stars. The spectrum exhibits a strong, degenerate dependence on the EOS, where the stiffening effect of the quarkyonic matter influences oscillation frequencies and damping times in a characteristic manner. We also demonstrate that $\omega$ mode frequencies for quarkyonic stars follow approximate universal relations, largely independent of the EOS.