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arXiv 1105.0368gr-qcastro-ph.HE
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紧天体双星并合中的引力波和非轴对称振荡模

Gravitational waves and nonaxisymmetric oscillation modes in mergers of compact object binaries

Nikolaos Stergioulas, Andreas Bauswein, Kimon Zagkouris, Hans-Thomas Janka

摘要:

研究了致密双星合并后非轴对称模的激发和伴随的引力波辐射。我们的分析是基于广义相对论模拟,在空间共形平坦近似下,使用光滑粒子流体力学的物质演化,我们使用一组相等和不等质量的模型,由两个非零温度强子状态方程和一个奇怪的恒星状态方程描述。通过对物质变量演化的傅里叶变换,我们可以识别出一些振荡模式,以及几个非线性分量(组合频率)。我们专注于占主导地位的m=2的模式,形成了一个三重态与两个非线性组件,耦合到准径向模式的结果。当致密天体的单个质量最有可能在1.2到1.35 $M_\odot$之间时,在引力波中可以识别出相应的三重频率。因此,通过直接分析流体的动力学,我们可以将引力波谱中的特定频率峰值与由m=2模式和准径向模式之间的差异引起的非线性分量相关联。一旦这些观测数据可用,就可以提取m=2和准径向模式频率,从而可以将引力波星震学应用于合并后的残余物,并对高密度物质的状态方程进行严格的限制。

英文摘要:

We study the excitation of nonaxisymmetric modes in the post-merger phase of binary compact object mergers and the associated gravitational wave emission. Our analysis is based on general-relativistic simulations, in the spatial conformal flatness approximation, using smoothed-particle-hydrodynamics for the evolution of matter, and we use a set of equal and unequal mass models, described by two nonzero-temperature hadronic equations of state and by one strange star equation of state. Through Fourier transforms of the evolution of matter variables, we can identify a number of oscillation modes, as well as several nonlinear components (combination frequencies). We focus on the dominant m=2 mode, which forms a triplet with two nonlinear components that are the result of coupling to the quasiradial mode. A corresponding triplet of frequencies is identified in the gravitational wave spectrum, when the individual masses of the compact objects are in the most likely range of 1.2 to 1.35 $M_\odot$. We can thus associate, through direct analysis of the dynamics of the fluid, a specific frequency peak in the gravitational wave spectrum with the nonlinear component resulting from the difference between the m=2 mode and the quasiradial mode. Once such observations become available, both the m=2 and quasiradial mode frequencies could be extracted, allowing for the application of gravitational-wave asteroseismology to the post-merger remnant and leading to tight constraints on the equation of state of high-density matter.

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