Anisotropic neutron stars with hyperons: implication of the recent nuclear matter data and observations of neutron stars

Abstract

Motivated by a recent report by Biwas and Bose (Phys Rev D 99:104002, 2019) that the observations of GW170817 to constrain the extent of pressure anisotropy in neutron stars within Bower–Liang anisotropic model, we systematically study the effects of anisotropic pressure on properties of the neutron stars with hyperons. The equation of state is calculated using the relativistic mean-field model with a BSP parameter set to determine nucleonic coupling constants and by using SU(6) and hyperon potential depths to determine hyperonic coupling constants. We investigate three models of anisotropic pressure known in literature namely Bowers and Liang (Astrophys J 88:657, 1974), Horvat et al. (Class Quant Grav 28:025009, 2011), and Cosenza et al. (J Math Phys (NY) 22:118, 1981). The reliability of the equation of state used is checked by comparing the parameters of the corresponding EOS to recent experimental data. The mass–radius, moment of inertia, and tidal deformability results of Bowers–Liang, Horvat et al., and Cosenza et al. anisotropic models are compared to the corresponding recent results extracted from the analysis of some NS observation data. We have found that the radii predicted by anisotropic NS are sensitive to the anisotropic model used and the results obtained by using the model proposed by Horvat et al. with anisotropic free parameter $$\varUpsilon ~\approx -$$Υ≈- 1.15 are relative compatible with all taken constraints.

Mass correction and deformation of slowly rotating anisotropic neutron stars based on Hartle–Thorne formalism

“…The same EOS has been used in several studies, e.g. [3,31,32]. The main differential equations in this work are Eqs.…”

“…Please see the discussion o the mass-radius relation of isotropic NS in Ref. [3]. It means that in anisotropic NS, the mass can increase by increasing anisotropic contribution and rotation.…”

“…Therefore, NSs are a e-mail: muhammad.lawrence@ui.ac.id (corresponding author) b e-mail: anto.sulaksono@sci.ui.ac.id the best avenues to study matter at high density and strongfield gravity simultaneously. However, up to now, NS's matter composition and gravity are not entirely understood [3,4]. We need to note that accurate measurements of massive pulsars have been reported in Refs.…”

“…For details, please see Refs. [3,21,[30][31][32][33] and please also see the references therein. We need to note that the anisotropic pressure might also exist in other kinds of compact stars, such as strange quark stars [34] and please also see the references therein.…”

Role of Anisotropy on the Tidal Deformability of Compact Stellar Objects

“…To calculate numerically the value of k 2 for a particular NS [22], one need to modify the master Equation (27) using the Equation (37) as ry + y 2 + (rR − 1)y + r 2 S = 0.…”