In this work, we study the impact of anisotropy on slowly rotating neutron stars by extending the Hartle–Thorne formalism in general relativity to include anisotropy in pressure up to second order in the angular velocity. We assess the presence of anisotropy within the star by employing a quasi-local relationship. Our results show that the ratio between the gravitational mass of the fastest anisotropic rotating configurations and the corresponding nonrotating ones ranges from 1.12 to 1.25, consistent with recent findings. We develop universal relations for the moment of inertia, binding energy, and quadrupole moment of the rotating stars. These relations are tested against various equations of state, which were modeled by a piecewise polytropic function with continuous sound speed.

中文翻译：

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具有参数化状态方程的缓慢旋转的各向异性中子星


在这项工作中，我们通过将广义相对论中的 Hartle-Thorne 形式扩展到包括角速度中高达二阶的压力各向异性，研究了各向异性对缓慢旋转的中子星的影响。我们通过采用准局部关系来评估恒星内各向异性的存在。我们的结果表明，最快的各向异性旋转配置与相应的非旋转配置的引力质量之比在 1.12 到 1.25 之间，这与最近的发现一致。我们为旋转恒星的惯性矩、束缚能和四极矩建立了通用关系。这些关系根据各种状态方程进行了测试，这些方程由具有连续声速的分段多方函数建模。