Anisotropic neutron stars with hyperons: implication of the recent nuclear matter data and observations of neutron stars
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Regular Article - Theoretical Physics
Anisotropic neutron stars with hyperons: implication of the recent nuclear matter data and observations of neutron stars A. Rahmansyah1,a , A. Sulaksono1,b , A. B. Wahidin1, A. M. Setiawan2 1 2
Departemen Fisika, FMIPA Universitas Indonesia, Kampus UI, Depok 16424, Indonesia Program Studi Pendidikan IPA, FMIPA Universitas Negeri Malang, Jl. Semarang 5, Malang 65145, Indonesia
Received: 14 May 2020 / Accepted: 14 August 2020 / Published online: 25 August 2020 © The Author(s) 2020
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 Υ ≈ − 1.15 are relative compatible with all taken constraints.
1 Introduction Neutron stars (NSs) are the perfect compact objects to study the matter at high densities and strong-field gravity simultaneously. However, both of the matter and the gravity of NSs still are not fully understood. a e-mail:
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b e-mail:
[email protected] (corresponding author)
There is tremendous progress related to NS properties observations such as mass, radius, and tidal deformation have been reported. Here we discuss shortly only some crucial ones. The accurate measurements of massive pulsars [1–5] provide maximum mass limit of NS around 2.0 M . There are also many studies reported the maximum mass of NSs from analyzing data extracted from gravitational wave (GW) events (see the recent review in Refs. [6,7], and the references therein). Note that Lim and Holt [7] discussed the Bayesian modeling of the nuclear equation of state (EOS) systematically, assuming a minimal model at high-density and neglect the possibility of phase transition for NS tidal deformability and GW170817 by generating 300000 NS EOSs by sampling from Bayesi
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