Radial oscillations in neutron stars from unified hadronic and quarkyonic equation of states

TL;DR

This paper investigates radial oscillations in neutron stars using unified hadronic and quarkyonic equations of state, analyzing mode frequencies and their dependence on the EoS and crust inclusion.

Contribution

It provides a comparative analysis of radial oscillation modes for neutron stars modeled with different unified EoSs, including hadronic and quarkyonic types, and examines the impact of crust on mode frequencies.

Findings

Lowest order mode frequency varies between EoS types at 1.4 M$_ ext{sun}$.

Mode frequency vanishes at maximum mass, indicating stability limits.

Crust inclusion significantly reduces higher-order mode frequencies.

Abstract

We study radial oscillations in non-rotating neutron stars by considering the unified equation of states (EoSs), which support the 2 M$_\odot$ star criterion. We solve the Sturm-Liouville problem to compute 20 lowest radial oscillation modes and their eigenfunctions for neutron star modelled with eight selected unified EoSs from distinct Skyrme-Hartree Fock, Relativistic Mean-Field and quarkyonic models. We compare the behavior of the computed eigenfrequency for NS modelled with hadronic to that with quarkyonic EoSs while varying central densities. The lowest order, f-mode frequency varies substantially between the two classes of the of EoS at 1.4 M$_\odot$ but vanishes at their respective maximum masses, consistent with the stability criterion $\partial M/\partial\rho_c > 0$. Moreover, we also computed large frequency separation and discovered that higher-order mode frequencies are significantly reduced by incorporating crust in the EoS.