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Abstrak :
Di alam semesta terdapat benda kompak yang merupakan sisa peluruhan dari evolusi bintang selama ratusan tahun. Salah satu benda kompak yang menarik untuk diteliti adalah bintang neutron. Karakteristik bintang neutron adalah ukurannya yang kecil dengan kerapatannya yang besar. Struktur bintang neutron didefinisikan dalam persamaan medan Einstein pada keadaan equilibrium yang disebut dengan persamaan Tolman,Oppenheimer dan Volkoff (TOV). Dalam keadaan isotropik, bintang neutron diasumsikan bersifat statis, bulat dan tidak berotasi. Penelitian mengenai bintang neutron dalam keadaan statik dan slow rotating sudah banyak dipelajari, namun penambahan efek konstanta kosmologi menjadi menarik untuk diteliti bagaimana pengaruhnya terhadap sifat bintang neutron. Pada keadaan slow rotating persamaan keadaan Einstein memiliki suku tambahan yang mengandung ω(r). Penambahan konstanta kosmologi (Λ) pada persamaan keadaan akan otomatis mengubah sifat bintang neutron. Perubahan terhadap massa-radius, momen inersia dan crust menjadi fokus yang dipelajari dalam penelitian ini. ......In the universe there are compact objects that are remnants of decay from the evolution of stars over hundreds of years. One compact object that is interesting to study is the neutron star. The characteristic of a neutron star is its small size and large density. The structure of a neutron star is defined in the Einstein field equation in a equilibrium state called the Tolman, Oppenheimer, and Volkoff (TOV) equation. In isotropic conditions, the neutron star is assumed to be static, spherical and not rotating. neutron star in static and slow rotating states have been widely studied, but the addition of the effects of cosmological constants is interesting to inverstigate how they affect the properties of neutron stars. In the slow rotating state, the Einstein state equation has an additional term containing ω(r). The addition of cosmological constants (Λ) to the state equation will automatically change the neutron stars nature. The changes of mass radius, moment of inertia and crust are the focus of this investigation.

Abstrak :
Summary: "The masses of neutron stars are limited by an instability to gravitational collapse, and an instability driven by gravitational waves limits their spin. Their oscillations are relevant to X-ray observations of accreting binaries and to gravitational wave observations of neutron stars formed during the coalescence of double neutron-star systems. This volume pulls together more than forty years of research to provide graduate students and researchers in astrophysics, gravitational physics, and astronomy with the first self-contained treatment of the structure, stability, and oscillations of rotating neutron stars. This monograph treats the equations of stellar equilibrium; key approximations, including slow rotation and perturbations of spherical and rotating stars; stability theory and its applications, from convective stability to the r-mode instability; and numerical methods for computing equilibrium configurations and the nonlinear evolution of their oscillations. The presentation of fundamental equations, results, and applications is accessible to readers who do not need the detailed derivations

Abstrak :
ABSTRAK
Tekanan Anisotropik dalam bintang neutron, dapat diselidiki dengan menentukan faktor anisotropiknya (σ) berdasarkan beberapa model. Model yang digunakan dalam penelitian ini adalah model dari Doneva-Yazadjiev (DY), Herrera-Barreto (HB), Bowers-Liang (BL), dan Hernandez-Nunez (HN). Pada inti bintang neutron diasumsikan tersusun dari nukleon, lepton dan hyperon. EOS materi bintang neutron dibangun menggunakan parameter set BSP dan simetri SU(6), yang selanjutnya dianalisis dengan persamaan TOV. Untuk model anisotropik DY, HB dan BL diperoleh prediksi massa maksimumnya konsisten dengan observasi massa dari PSR J1614-2230 dan PSR J0348+0432. Sedangkan untuk model HN, prediksi massa maksimum tidak dapat dicapai karena faktor anisotropiknya tidak konsisten seperti model DY, HB dan BL.

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ABSTRACT
The presence of anisotropic pressure in neutron stars can be investigate by establishing anisotropic factor (σ) based on the Doneva-Yazadjiev (DY), Herrera-Barreto (HB), Bowers-Liang (BL), and Hernandez-Nunez (HN) anisotropic models. We assume that the neutron stars matter consist of nucleons, leptons, and hyperons. EOS neutron stars matter built by BSP Parameter set and SU(6) symmetry, and then analyzed by TOV equations. We obtain that the DY, HB, and BL models predict neutron stars maximum mass consistent with PSR J1614-2230 and PSR J0348+0432. But the HN model failed to predict neutron stars maximum mass because the anisotropic factor of this model is inconsistent like the others

Abstrak :
Teori gravitasi Eddington-inspired Born Infeld EiBI menyediakan ranah baru untuk kopling antara gravitasi-materi di luar relativitas umum Einstein. Kopling gravitasi-materi dipandang sebagai kontribusi anisotropik tambahan terhadap relativitas umum Einstein pada bintang. Struktur bintang dipelajari untuk persamaan keadaan bintang neutron politropik dan bintang neutron realistis. Massa dan radius bintang pada EiBI dengan materi anisotropik untuk ekspansi ? orde rendah mendekati struktur EiBI standar dengan kopling pada materi isotropik. Batas ? agar memenuhi kriteria bintang anisotropik bergantung pada stiffness persamaan keadaan bintang. Berdasarkan pendekatan ini, singularitas skalar Ricci dan Kretschmann tidak ditemukan di permukaan bintang. ......Eddington inspired Born Infeld theory of gravity EiBI provides a new playground for gravity matter coupling beyond general relativity GR . In this manuscript, I consider gravity matter coupling in EiBI as an additional anisotropic contribution to GR on stars. I show that for low order series expansion of parameter the structure of star are close to original theory. I also investigate some criteria for anisotropic star structure in this theory for polytropic and realistic neutron star equation of state EoS . The constraint of depends on the stiffness of EoS. Based on this approach, the singularity of Ricci and Kretschmann curvature scalar are not found at the surface of the star for first and second order expansion in this theory.