Oscillation Modes and Gravitational Waves from Strangeon Stars

TL;DR

This paper investigates the oscillation modes of strangeon stars using a phenomenological model, revealing unique properties and potential gravitational wave signatures that differ from neutron stars, aiding in understanding dense matter physics.

Contribution

First study of oscillation modes in strangeon stars using a Lennard-Jones EOS, providing insights into their gravitational wave signatures and universal relations.

Findings

Radial oscillation properties differ from neutron stars, especially at low densities.

$f$-mode frequencies range from 6.7 kHz to 8.7 kHz.

Universal relations between $f$-mode frequency and star properties established.

Abstract

The strong interaction at low energy scales determines the equation of state (EOS) of supranuclear matters in neutron stars (NSs). It is conjectured that the bulk dense matter may be composed of strangeons, which are quark clusters with nearly equal numbers of $u$, $d$, and $s$ quarks. To characterize the strong-repulsive interaction at short distance and the nonrelativistic nature of strangeons, a phenomenological Lennard-Jones model with two parameters is used to describe the EOS of strangeon stars (SSs). For the first time, we investigate the oscillation modes of non-rotating SSs and obtain their frequencies for various parameterizations of the EOS. We find that the properties of radial oscillations of SSs are different from those of NSs, especially for stars with relatively low central energy densities. Moreover, we calculate the $f$-mode frequency of nonradial oscillations of SSs within the relativistic Cowling approximation. The frequencies of the $f$-mode of SSs are found to be in the range from $6.7\,$kHz to $ 8.7\,\rm{kHz}$. Finally, we study the universal relations between the $f$-mode frequency and global properties of SSs, such as the compactness and the tidal deformability. The results we obtained are relevant to pulsar timing and gravitational waves, and will help to probe NSs' EOSs and infer nonperturbative behaviours in quantum chromodynamics.