Higher-order symmetry energy and neutron star core-crust transition with Gogny forces

2017/06/30 by C. Gonzalez-Boquera, M. Centelles, X. Viñas +1 · 2 citations
Physics and Astronomy · #nucl-th #astro-ph.SR

paper · pdf · doi:10.1103/physrevc.96.065806

published as Phys. Rev. C 96, 065806 (2017) · 24 pages, 15 figures, discussions and bibliography updated, to appear in Physical Review C

arxiv created 2017/12/19 · arxiv updated 2017/12/27

Abstract

We study the symmetry energy and the core-crust transition in neutron stars using the finite-range Gogny nuclear interaction and examine the deduced crustal thickness and crustal moment of inertia. We start by analyzing the second-, fourth- and sixth-order coefficients of the Taylor expansion of the energy per particle in powers of the isospin asymmetry for Gogny forces. These coefficients provide information about the departure of the symmetry energy from the widely used parabolic law. The neutron star core-crust transition is evaluated by looking at the onset of thermodynamical instability of the liquid core. The calculation is performed with the exact (i.e., without Taylor expansion) Gogny EoS for the core, and also with its Taylor expansion in order to assess the influence of isospin expansions on locating the inner edge of neutron star crusts. It is found that the properties of the core-crust transition derived from the exact EoS differ from the predictions of the Taylor expansion even when the expansion is carried through sixth order in the isospin asymmetry. Gogny forces, using the exact EoS, predict the ranges 0.094 fm^-3 \lesssim ρ_t \lesssim 0.118 fm^-3 for the transition density and 0.339 MeV fm^-3 \lesssim P_t \lesssim 0.665 MeV fm^-3 for the transition pressure. The transition densities show an anticorrelation with the slope parameter L of the symmetry energy. The transition pressures are not found to correlate with L. Neutron stars obtained with Gogny forces have maximum masses below 1.74M_\odot and relatively small moments of inertia. The crustal mass and moment of inertia are evaluated and comparisons are made with the constraints from observed glitches in pulsars.

Cited by

• Neutron-rich matter in atomic nuclei and neutron stars
• An effective finite-range Gogny-type interaction for the quantum molecular dynamics like model

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