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arXiv 0908.3474astro-ph.SR
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超新星爆炸混合不稳定性的三维模拟

Three-Dimensional Simulations of Mixing Instabilities in Supernova Explosions

N. J. Hammer, H. -Th. Janka, E. Mueller

摘要:

我们提出了第一个三维(3D)模拟的大规模混合发生在冲击加热的恒星层喷射在爆炸的15.5太阳质量的蓝超巨星。超新星激波从发射开始就伴随着中微子加热,直到核心坍缩后两个多小时才从恒星表面爆发。剧烈的对流翻转后的冲击层导致爆炸开始与显着的非球面性,这触发了瑞利-泰勒(RT)不稳定性的增长在爆炸的恒星的组成界面。发现了氢(H)的深层向内混合,以及快速移动的富含金属的团块以高速穿透到恒星的H包层,如观察到的,SN 1987 A的情况下。在某些模型中,还可以得到含有相当大一部分喷射出的铁族元素(高达几个0.001太阳质量)的单个团块。前驱体的金属芯部分翻转,其中Ni主导的指状物超过富氧子弹,并且Ni和O两者都在来自碳层的材料的前面移动。与相应的2D比较(轴对称)计算,我们确定RT指的生长更快,在He和H层中密集的金属携带团的减速减小,在H壳层中的渐近团速度更高(对于所考虑的先驱体,高达~4500 km/s,爆炸能量为10^{51}尔格,而不是2D中的<2000 km/s),重元素的向外径向混合和氢的向内混合在3D中比在2D中更有效。我们提出了一个简单的参数,解释这些结果作为结果的不同行动的阻力在两个几何形状的移动物体。(节略)

英文摘要:

We present the first three-dimensional (3D) simulations of the large-scale mixing that takes place in the shock-heated stellar layers ejected in the explosion of a 15.5 solar-mass blue supergiant star. The outgoing supernova shock is followed from its launch by neutrino heating until it breaks out from the stellar surface more than two hours after the core collapse. Violent convective overturn in the post-shock layer causes the explosion to start with significant asphericity, which triggers the growth of Rayleigh-Taylor (RT) instabilities at the composition interfaces of the exploding star. Deep inward mixing of hydrogen (H) is found as well as fast-moving, metal-rich clumps penetrating with high velocities far into the H-envelope of the star as observed, e.g., in the case of SN 1987A. Also individual clumps containing a sizeable fraction of the ejected iron-group elements (up to several 0.001 solar masses) are obtained in some models. The metal core of the progenitor is partially turned over with Ni-dominated fingers overtaking oxygen-rich bullets and both Ni and O moving well ahead of the material from the carbon layer. Comparing with corresponding 2D (axially symmetric) calculations, we determine the growth of the RT fingers to be faster, the deceleration of the dense metal-carrying clumps in the He and H layers to be reduced, the asymptotic clump velocities in the H-shell to be higher (up to ~4500 km/s for the considered progenitor and an explosion energy of 10^{51} ergs, instead of <2000 km/s in 2D), and the outward radial mixing of heavy elements and inward mixing of hydrogen to be more efficient in 3D than in 2D. We present a simple argument that explains these results as a consequence of the different action of drag forces on moving objects in the two geometries. (abridged)

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