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⊙ star criterion. We solve the Sturm–Liouville problem to compute the 20 lowest radial oscillation modes and their eigenfunctions for a neutron star modeled 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 an NS modeled with hadronic to one with quarkyonic EoSs while varying the central densities. The lowest-order f-mode frequency varies substantially between the two classes of the EoS at 1.4 M⊙ but vanishes at their respective maximum masses, consistent with the stability criterion ∂M/∂ρc>0. Moreover, we also compute large frequency separation and discover that higher-order mode frequencies are significantly reduced by incorporating a crust in the EoS.

Radial oscillations of hybrid stars and neutron stars including delta baryons: the effect of a slow quark phase transition

“…In this work, we investigate radial oscillations of NSs with different hadronic matter compositions, such as hyperons and delta baryons, followed by a phase transition to quark matter. Numerous studies delved into the radial oscillations of neutron stars (NSs) featuring diverse exotic phases, such as dark matter and deconfined quark matter [39,[41][42][43][44][45][46][47]. In our prior research [48], we focused on the radial oscillations of hadronic matter containing hyperons and ∆ baryons.…”

“…However, the radial oscillation for the lowest order mode (n = 0) is not greatly impacted by the crust because it typically accounts for less than 10% of the stellar radius and the oscillation nodes are situated far inside the NS core. But other high oscillation modes are present in the crust of the star and hence the eigenfrequencies are modified (characterized by the peaks in the ∆ν n ) [43,48].…”

Probing the impact of delta-baryons on nuclear matter and non-radial oscillations in neutron stars

“…the dimensionless tidal deformability (Λ) and the non-radial f -mode oscillations. Radial oscillations in NSs for different matter compositions has been an active area of study [19,20,[116][117][118][119] with the matter composition being recently extended to include ∆-resonances as well [18]. Through this work we are proceeding further by studying, for the first time, nonradial f -mode oscillations in NSs with ∆-admixed hypernuclear as well as hyperon-free matter.…”

“…These oscillations are categorized into two primary types: radial and non-radial, both of which are subjects of active research. Radial oscillations involve expansions and contractions akin to a pulsating motion that helps maintain the star's spherical shape [17][18][19][20][21]. In contrast, non-radial oscillations manifest as asymmetric vibrations centered around the star's core are guided by a restoring force that brings the star back to its equilibrium state [9][10][11][22][23][24][25][26][27].…”

The impact of anisotropy on neutron star properties: insights from 𝖨–𝖿–𝖢 universal relations

“…Neutron stars (NSs) exhibit oscillations that are regarded as potential sources of GWs, manifesting in various forms including radial [8][9][10][11][12][13] and non-radial [14][15][16][17] modes. When a NS experiences external or internal disturbances, it emits GWs through different oscillation modes known as quasi-normal modes (QNMs), each characterized by the restoring force that brings them back to their equilibrium state.…”