Incompressibility and symmetry energy of a neutron star

We trace a systematic and consistent method to precisely numerate the magnitude range for various structural and isospin compositional properties of the neutron star. Incompressibility, symmetry energy, slope parameter, and curvature of a neutron star are investigated using the relativistic energy density functional within the framework of coherent density fluctuation model. The analytical expression for the energy density functional of the neutron star matter is motivated from the Brückner functional and acquired by the polynomial fitting of the saturation curves for three different relativistic mean-field parameter sets (NL3, G3, and IU-FSU). The modified functional is folded with the neutron star's density-dependent weight function to calculate the numerical values for incompressibility and symmetry energy using the coherent density fluctuation model. The NL3 parameter set, being the stiffest equation of state, has a higher magnitude of all the properties compared to the other two parameter sets.

Figure 1

The neutron star matter saturation curves as a function of baryon number density for different asymmetry $\alpha =\frac{n_n-n_p}{n_n+n_p}$ parameter. The solid curve represents the RMF numerical data and the dotted black curve stands for the fitted expression.

Figure 2

Mass-radius profile of a neutron star for NL3 (red), G3 (green), and IU-FSU (blue) parameter sets. The old NICER data is given in two boxes from the two different analyses [67, 68]. The horizontal line in violet color represents the new NICER constraint on the radius of the canonical star [69].

Figure 3

The neutron star densities ($\rho$) for NL3 (red), G3 (green), and IU-FSU (blue) parameter sets as a function of radius of the maximum mass star ($R$). The mass numbers ($A$) of the maximum mass neutron star for NL3, G3, and IU-FSU are $3.35\times {10}^{54}, 2.32\times {10}^{54}$, and $2.23\times {10}^{54}$ respectively.