标题： 合并中子星——迈向物理模型的一步。 I. 流体动力学演化和引力波辐射 显示英文标题

标题： Coalescing Neutron Stars -- a Step Towards Physical Models. I. Hydrodynamic Evolution and Gravitational-Wave Emission

摘要： 我们研究合并中子星的动力学和演化过程。 尽管代码（分段抛物线方法）完全是牛顿的，但我们包括了引力波的发射及其对流体动力学流动的反作用。 中子星物质的性质由Lattimer & Swesty（1991）的物理状态方程描述。 通过一个精细的“中微子泄漏方案”，考虑了所有类型中微子的能量损失以及由于电子中微子和反中微子的发射导致的电子分数变化。 我们模拟了两个相同、冷却的中子星的合并，其重子质量为$\approx\!1.6\,M_\odot$，半径为$\approx\!15$~km，并且初始中心间距离为42~km。 密度和电子浓度的初始分布来自一个冷中子星的静力平衡模型（中心温度约为$8\,{\rm MeV}$）。 我们研究了三种情况，这三种情况根据中子星中的初始速度分布不同，代表了中子星自转相对于轨道角动量矢量方向的不同情况。 在约1毫秒内，中子星合并成一个快速旋转（$P_{\rm spin}\approx 1$毫秒）、高密度物体（$\rho\approx 10^{14}$克/立方厘米$^3$），并伴有周围密度为$\rho\approx 10^{10}-10^{12}$克/立方厘米$^3$的厚盘，轨道速度约为0.3--0.5倍光速。 在本工作中，我们使用四极近似详细评估了模型的引力波辐射。 在即将发表的论文中，我们将集中研究中微子辐射及其对伽马射线暴的影响。 最大亮度超过$10^{55}$erg/s，在约1毫秒内达到。 显示英文摘要

摘要： We investigate the dynamics and evolution of coalescing neutron stars. Although the code (Piecewise Parabolic Method) is purely Newtonian, we do include the emission of gravitational waves and their backreaction on the hydrodynamic flow. The properties of neutron star matter are described by the physical equation of state of Lattimer \& Swesty (1991). Energy loss by all types of neutrinos and changes of the electron fraction due to the emission of electron neutrinos and antineutrinos are taken into account by an elaborate ``neutrino leakage scheme''. We simulate the coalescence of two identical, cool neutron stars with a baryonic mass of $\approx\!1.6\,M_\odot$ and a radius of $\approx\!15$~km and with an initial center-to-center distance of 42~km. The initial distributions of density and electron concentration are given from a model of a cold neutron star in hydrostatic equilibrium (central temperature about $8\,{\rm MeV}$). We investigate three cases which differ by the initial velocity distribution in the neutron stars, representing different cases of the neutron star spins relative to the direction of the orbital angular momentum vector. Within about 1~ms the neutron stars merge into a rapidly spinning ($P_{\rm spin}\approx 1$~ms), high-density body ($\rho\approx 10^{14}$~g/cm$^3$) with a surrounding thick disk of material with densities $\rho\approx 10^{10}-10^{12}$~g/cm$^3$ and orbital velocities of~0.3--0.5~c. In this work we evaluate the models in detail with respect to the gravitational wave emission using the quadrupole approximation. In a forthcoming paper we will concentrate on the neutrino emission and implications for gamma-ray bursters. A maximum luminosity in excess of $10^{55}$~erg/s is reached for about 1~ms.