Imprints of high-density nuclear symmetry energy on the crustal fraction of neutron star moment of inertia

TL;DR

This paper investigates how the density dependence of nuclear symmetry energy affects the crustal fraction of neutron star moment of inertia, providing insights into the equation of state of dense neutron-rich matter.

Contribution

It introduces an isospin-dependent parameterization of neutron star EOS to analyze the impact of symmetry energy parameters on crustal moment of inertia fractions.

Findings

Symmetry energy parameters significantly influence the crustal moment of inertia fraction.

Increased slope $L$ and skewness $J_{sym}$ lead to larger $rac{ riangle I}{I}$.

Higher curvature $K_{sym}$ reduces $rac{ riangle I}{I}$.

Abstract

The density dependence of nuclear symmetry energy $E_{\rm sym}(\rho)$ remains the most uncertain aspect of the equation of state (EOS) of supradense neutron-rich nucleonic matter. Implications of observational crustal fraction of neutron star (NS) moment of inertia $\Delta I/I$ on the $E_{\rm sym}(\rho)$ are examined in the present work, utilizing an isospin-dependent parameterization of NS EOS. We find that symmetry energy parameters significantly influence the $\Delta I/I$, while the EOS of symmetric nuclear matter has a negligible effect. An increase in the slope $L$ and skewness $J_{\rm sym}$ of symmetry energy results in a larger $\Delta I/I$, whereas an increase in the curvature $K_{\rm sym}$ leads to a reduction in $\Delta I/I$. Additionally, we discuss the imprints of observational $\Delta I/I$ on the symmetry energy for NSs with masses of 1.0 M$_\odot$ or 1.4 M$_\odot$. Our results indicate that the $\Delta I/I$ has the potential to set a lower limit of symmetry energy at densities exceeding $3\rho_0$, particularly when $L$ is constrained to values less than $60$ MeV, thereby enhancing our understanding of supradense NS matter.