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

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.