Constraining the surface curvature of an anisotropic neutron star

Abstract

The anisotropy of pressure arises due to the various complex phenomena that happen inside the neutron star (NS). In this study, we calculate the degree of anisotropy inside the NS using the scalar pressure anisotropy model. Macroscopic properties such as mass, radius, compactness, redshift, tidal deformability, the moment of inertia, and surface curvature (SC) are computed for the anisotropic NS with the equation of states spanning from relativistic to nonrelativistic cases. The variation of SC as the functions of the above-mentioned quantities are computed by changing the degree of anisotropy. Pressure anisotropy has significant effects on the magnitude of SC. The relations between the canonical $\mathrm{SC}\ensuremath{-}\mathrm{\ensuremath{\Lambda}}$ and $\mathrm{SC}\ensuremath{-}\overline{I}$ are studied. From the GW170817 tidal deformability data, we constraints the magnitude of SC are found to be ${\mathrm{SC}}_{1.4}({10}^{14})={3.44}_{\ensuremath{-}1.0}^{+0.4},{2.85}_{\ensuremath{-}1.20}^{+0.62},{2.52}_{\ensuremath{-}1.02}^{+0.61}$ for ${\ensuremath{\lambda}}_{\mathrm{BL}}=0.0$, 1.0, and 2.0, respectively.