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arXiv 1608.01048astro-ph.HEnucl-th
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质子中子星的引力波星震学

Gravitational wave asteroseismology with protoneutron stars

Hajime Sotani, Tomoya Takiwaki

摘要:

利用一维核塌缩超新星数值模拟结果,在相对论线性微扰理论框架下研究了引力波在反弹后的频率随时间的演化.本文建立了质子中子星模型,使质子中子星的质量和半径与数值模拟结果等价。然后,我们发现质子中子星辐射的引力波的频率强烈地依赖于质子中子星的质量和半径,但几乎与星内电子分数和每重子熵的分布无关。此外,我们还发现,无论是哪种原型,引力波的频率都可以用质子中子星平均密度的平方根来表征,这与冷中子星的经验公式完全不同。谱对质量和半径的依赖性不同于$g$模:由于对流和吸积激波不稳定性引起的质子中子星表面的振荡。对这些引力波模的仔细观测可以确定核反弹后质子中子星的质量和半径的演化。此外,引力波的预期频率在反弹后的早期阶段约为几百赫兹,这必须是地基引力波探测器的良好候选者。

英文摘要:

We examine the time evolution of the frequencies of the gravitational wave after the bounce within the framework of relativistic linear perturbation theory using the results of one dimensional numerical simulations of core-collapse supernovae. Protoneutron star models are constructed in such a way that the mass and radius of protoneutron star become equivalent to the results obtained from the numerical simulations. Then, we find that the frequencies of gravitational waves radiating from protoneutron stars strongly depend on the mass and radius of protoneutron stars, but almost independently of the profiles of electron fraction and entropy per baryon inside the star. Additionally, we find that the frequencies of gravitational waves can be characterized by the square root of the average density of protoneutron star irrespectively the progenitor models, which are completely different from the empirical formula for cold neutron stars. The dependence of the spectra on the mass and radius is different from that of the $g$-mode: the oscillations around the surface of protoneutron stars due to the convection and the standing accretion-shock instability. Careful observations of the these modes of gravitational waves can determine the evolution of the mass and radius of protoneutron stars after core-bounce. Furthermore, the expected frequencies of gravitational waves are around a few hundred hertz in the early stage after bounce, which must be a good candidate for the ground-based gravitational wave detectors.

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