Coalescing neutron stars -A step towards physical models - III. Improved numerics and different neutron star masses and spins
Coalescing neutron stars -A step towards physical models - III. Improved numerics and different neutron star masses and spins
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DOI：
10.1051/0004-6361:20011453
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发表时间：
2001-06
影响因子：
6.5
通讯作者：
M. Ruffert;H. Janka
中科院分区：
文献类型：
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作者：
M. Ruffert;H. Janka
在这篇文章中，我们汇编了我们最先进的中子星合并模拟的结果，包括对所采用的数值过程的描述，以及对大量计算模型的更完整的概述。用基于分段抛物线方法的程序进行了三维水动力模拟，最多可嵌套五层笛卡尔网格。模拟基本上是牛顿的，但考虑了引力波的发射和相应的反反应。物理核态方程的使用使我们能够跟踪恒星介质的热力学历史，并计算由于中微子发射而造成的能量和轻子数损失。关于中子星的质量和质量比、中子星的自转、用最细网格单元大小和网格能级数表示的数值分辨率，以及从熵方程而不是能量方程的解来计算温度，计算模型是不同的。我们的模拟表明，引力波发射的细节仍然对数值分辨率敏感，即使在我们最高质量的计算中也是如此。中子星合并可以抛出的质量很大程度上取决于系统的角动量。我们的结果不支持在最近的工作中假设的温度和质子与核子比的初始条件，以产生A约130峰周围和以上的原子核的太阳r过程图案。改进的模型证实了我们之前的结论，即在两颗中子星合并的动力学阶段，伽马射线暴不是由中微子发射提供动力的。
(Abridged) In this paper we present a compilation of results from our most advanced neutron star merger simulations, including a description of the employed numerical procedures and a more complete overview over a large number of computed models. The three-dimensional hydrodynamic simulations were done with a code based on the Piecewise Parabolic Method with up to five levels of nested Cartesian grids. The simulations are basically Newtonian, but gravitational-wave emission and the corresponding back-reaction are taken into account. The use of a physical nuclear equation of state allows us to follow the thermodynamic history of the stellar medium and to compute the energy and lepton number loss due to the emission of neutrinos. The computed models differ concerning the neutron star masses and mass ratios, the neutron star spins, the numerical resolution expressed by the cell size of the finest grid and the number of grid levels, and the calculation of the temperature from the solution of the entropy equation instead of the energy equation. Our simulations show that the details of the gravitational-wave emission are still sensitive to the numerical resolution, even in our highest-quality calculations. The amount of mass which can be ejected from neutron star mergers depends strongly on the angular momentum of the system. Our results do not support the initial conditions of temperature and proton-to-nucleon ratio assumed in recent work for producing a solar r-process pattern for nuclei around and above the A approx 130 peak. The improved models confirm our previous conclusion that gamma-ray bursts are not powered by neutrino emission during the dynamical phase of the merging of two neutron stars.