Spin-polarized $\beta$-stable neutron star matter: the nuclear symmetry energy and GW170817 constraint

Abstract

Magnetic field of rotating pulsar might be so strong that the equation of state (EOS) of neutron star (NS) matter is significantly affected by the spin polarization of baryons. In the present work, the EOS of the spin-polarized nuclear matter is investigated in the nonrelativistic Hartree-Fock formalism, using a realistic density dependent nucleon-nucleon interaction with its spin and spin-isospin dependence accurately adjusted to the Brueckner-Hartree-Fock results for the spin-polarized nuclear matter. The nuclear symmetry energy and proton fraction are found to increase significantly with the increasing spin polarization of baryons, leading to a larger probability of the direct Urca process in the cooling of magnetar. The EOS of the $\beta$-stable np$e\mu$ matter obtained at different spin polarizations of baryons is used as the input for the Tolman-Oppenheimer-Volkov equations to determine the hydrostatic configuration of NS. Based on the GW170817 constraint on the radius $R_{1.4}$ of NS with $M\approx 1.4_{\odot }$, our mean-field results show that up to $60\%$ of baryons in the NS merger might be spin-polarized. This result supports the magnetar origin of the blue kilonova ejecta of GW170817 suggested by Metzger et al., and the spin polarization of baryons needs, therefore, to be properly treated in the many-body calculation of the EOS of NS matter before comparing the calculated NS mass and radius with those constrained by the multi-messenger GW170817 observation.

Misprints corrected; published in Physical Review C 102, 045809 (2020)

References in corpus (11)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Shapiro delay measurement of a two solar mass neutron star
• A Massive Pulsar in a Compact Relativistic Binary
• Multi-messenger Observations of a Binary Neutron Star Merger
• Neutron Star Observations: Prognosis for Equation of State Constraints
• Swift and NuSTAR observations of GW170817: detection of a blue kilonova
• The Giant Dipole Resonance as a quantitative constraint on the symmetry energy
• Nuclear rainbow scattering and nucleus-nucleus potential
• Equation of state of the neutron star matter, and the nuclear symmetry energy
• Folding model study of the isobaric analog excitation: isovector density dependence, Lane potential and nuclear symmetry energy
• Role of Landau-Rabi quantization of electron motion on the crust of magnetars within the nuclear energy density functional theory

Cited by in corpus (2)

• Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817
• Probing high-density nuclear symmetry energy with ${\Xi }^{-}/{\Xi }^0$ ratio in heavy-ion collisions at $\sqrt{s_{NN}}\sim 3$ GeV