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arXiv 2112.09474astro-ph.HEgr-qc
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伪牛顿引力下的中子星振荡

Neutron star oscillations in pseudo-Newtonian gravity

Yat-To Tang, Lap-Ming Lin

AI总结:

本研究使用纯牛顿方法和三种伪牛顿形式研究中子星振荡,发现Zha等人提出的“Case A+lapse”形式能将1.4太阳质量中子星的基本径向模式频率近似到百分之几十以内,并将非径向四极f模式频率近似到百分之几以内。

摘要:

我们使用纯牛顿方法和另外三种伪牛顿形式研究中子星的振荡。我们的工作动机是伪牛顿形式常用于核心坍缩超新星(CCSN)模拟。我们使用修正的牛顿流体力学方程和引力势的不同组合,推导并数值求解了中子星振荡的径向和非径向微扰方程。我们特别关注 Zha 等人 [Phys. Rev. Lett. 125, 051102 (2020)] 最近提出的形式,该形式在 CCSN 模拟中实现了标准 Case A 有效势,并对流体力学方程进行了额外的 lapse 函数修正。我们发现,对于我们选择的 EOS 模型,这种“Case A+lapse”形式通常能将广义相对论中计算得到的 $1.4 M_\odot$ 中子星基本径向模式频率近似到约百分之几十以内。对于预期对原中子星发射的引力波有强烈贡献的非径向四极 $f$ 模式,Case A+lapse 形式的表现要好得多,即使在广义相对论的最大质量构型下,也能将 $f$ 模式频率近似到约百分之几以内。

英文摘要:

We investigate the oscillations of neutron stars using a purely Newtonian approach and three other pseudo-Newtonian formulations. Our work is motivated by the fact that pseudo-Newtonian formulations are commonly used in core-collapse supernova (CCSN) simulations. We derive and solve numerically the radial and nonradial perturbation equations for neutron star oscillations using different combinations of modified Newtonian hydrodynamics equations and gravitational potentials. We pay special attention to the formulation proposed recently by Zha et al. [Phys. Rev. Lett. 125, 051102 (2020)] that implements the standard Case A effective potential in CCSN simulations with an additional lapse-function correction to the hydrodynamics equations. We find that this "Case A+lapse" formulation can typically approximate the frequency of the fundamental radial mode of a $1.4 M_\odot$ neutron star computed in general relativity to about a few tens of percent for our chosen EOS models. For the nonradial quadrupolar $f$ mode, which is expected to contribute strongly to the gravitational waves emitted from a protoneutron star, the Case A+lapse formulation performs much better and can approximate the $f$ mode frequency to within about a few percent even for the maximum-mass configuration in general relativity.

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