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arXiv · 2209.02861

Massive neutron stars with small radii in relativistic mean-field models optimized to nuclear ground states

Tsuyoshi Miyatsu·Myung-Ki Cheoun·Kyungsik Kim·Koichi Saito
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Abstract

We present an equation of state (EoS) for neutron stars using the relativistic mean-field model with isoscalar- and isovector-meson mixing. Taking into account the results of the neutron skin thickness, $R_{\rm skin}$, of $^{208}$Pb reported by the PREX collaboration, the dimensionless tidal deformability of a canonical neutron star observed from GW170817, and a $2.6$ $M_{\odot}$ compact star implied by the secondary component of GW190814, a new effective interaction is constructed so as to reproduce the saturation condition of nuclear matter and the ground-state properties of finite, closed-shell nuclei. We find that the neutron star EoS exhibits the rapid stiffening around twice the nuclear saturation density, which is caused by the soft nuclear symmetry energy, $E_{\rm sym}$. It is also noticeable that the thick $R_{\rm skin}$ from the PREX-2 experiment can be achieved with the small slope parameter of $E_{\rm sym}$ stemming from the isoscalar-meson mixing. Thus, we speculate that the secondary component of GW190814 is the heaviest neutron star ever discovered.

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Tsuyoshi Miyatsu, Myung-Ki Cheoun, Kyungsik Kim, Koichi Saito. 2022-09-06. Massive neutron stars with small radii in relativistic mean-field models optimized to nuclear ground states. https://arxiv.org/abs/2209.02861

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