Higher-order symmetry energy parameters and neutron star properties

We discuss the constraints on the higher-order symmetry energy parameters and neutron star radii based on the experimentally constrained range of the symmetry energy parameters (S₀, L) and the existence of massive neutron stars. We apply the nuclear matter equation of state (EOS) given in the Fermi momentum expansion with coefficients determined by the saturation and symmetry energy parameters [1]. By using experimentally constrained values of n₀, E₀, K₀, S₀, L, and the correlation of K_n and Q_n with L found in theoretical model EOSs [1], we find that the 1.4 M_sun neutron star radius is found to be in the range R=(10.6-12.2) km as long as we require that the 2 M_sun neutron stars are supported. This range is consistent with the gravitational wave observation from GW170817 [2]. We also find a constraint on the third order derivative parameter (Q_n) from the existence of 2 M_sun neutron stars.

[1] I. Tews, J. M. Lattimer, A. Ohnishi, E. E. Kolomeitsev, Astrophys. J. 848 (2017), 105.
[2] B. P. Abbott et al. (LIGO Scientific and Virgo Collab.), Phys. Rev. Lett. 119 (2017), 161101.