磁化中子星的新普适关系
New Universal Relations for Magnetized Neutron Stars
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中文总结 AI 辅助
本文针对磁化中子星，经二阶微扰处理磁场效应，发现磁偶极矩与恒星致密性的精确普适关系，及磁偶极矩、磁场诱导四极矩与椭率的近似普适关系，相关关系可用于磁化中子星双天体引力波信号分析。
中文摘要 AI 辅助
与中子星质量-半径关系（该关系通过致密核物质的物态方程敏感依赖于恒星内部结构）不同，某些中子星性质遵循近似普适关系，这类关系仅对物态方程表现出弱依赖性。本文探究磁化中子星的新普适关系，聚焦于纯极型偶极磁场构型，并将磁场效应按场强的二阶微扰处理。在通过恒星质量和极区磁场强度对相关量进行恰当归一化后，我们首先确定了磁偶极矩与恒星致密性之间的精确普适关系；随后发现磁偶极矩、磁场诱导的恒星四极矩与椭率之间的近似普适关系，其物态方程导致的分数变化处于O(10%)量级。我们用牛顿多方球的解析估计支持这些数值结果，该估计再现了观测到的行为。在新发现的关系中，连接磁偶极矩与恒星四极矩的关系对含磁化中子星的双天体引力波信号分析可能尤为有用。
英文摘要
Unlike the neutron-star mass--radius relation, which depends sensitively on the internal stellar structure through the equation of state of dense nuclear matter, certain neutron-star properties obey approximately universal relations that exhibit only weak dependence on the equation of state. In this paper, we explore new universal relations for magnetized neutron stars. We focus on a purely poloidal dipolar magnetic-field configuration and treat the effects of the magnetic field perturbatively to second order in the field strength. After appropriately normalizing the relevant quantities by the stellar mass and the magnetic-field strength at the pole, we first identify an exact universal relation between the magnetic dipole moment and stellar compactness. We then find approximate universal relations among the magnetic dipole moment, magnetically-induced stellar quadrupole moment, and ellipticity, with fractional variations due to the equation of state at the level of O(10%). We support these numerical findings with analytic estimates for Newtonian polytropes, which reproduce the observed behavior. Among the newly discovered relations, the one connecting the magnetic dipole moment and stellar quadrupole moment may be particularly useful for the analysis of gravitational-wave signals from binaries containing magnetized neutron stars.
