Light-Element Production in the Circumstellar Matter of Energetic Type Ic Supernovae
Light-Element Production in the Circumstellar Matter of Energetic Type Ic Supernovae
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DOI：
10.1086/505176
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发表时间：
2006-01
期刊：
影响因子：
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通讯作者：
K. Nakamura;S. Inoue;S. Wanajo;T. Shigeyama
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文献类型：
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作者：
K. Nakamura;S. Inoue;S. Wanajo;T. Shigeyama
我们调查充满活力的Ic型超新星作为生产网站的6Li和Be在银河系的早期阶段。最近的观测显示，一些[Fe/H] < -2.5的贫金属恒星拥有出乎意料的高丰度6Li。有些还表现出Be和N的丰度增加。从理论的角度来看，最近对贫金属大质量恒星演化的研究表明，旋转引起的混合可以使外层H和He层富含C，N和O（CNO）元素，特别是N，同时导致这些层的强烈质量损失。在这里，我们考虑高能超新星爆炸发生后，祖星星已经失去了所有，但一小部分的He层。由He和CNO组成的超新星喷出物的最快部分和星周物质（CSM）可以直接相互作用，通过氦核聚变和氦-氦聚变反应产生轻元素。CSM应该足够厚，以便高能粒子的相互作用终止在其最里面的区域。我们计算了由此产生的6Li/O和9 Be/O的比例在喷出物+ CSM材料，其中非常贫金属的恒星可能形成。我们发现，如果保留在爆炸前的核心的He层的质量是~0.01-0.1 M的反馈，如果在He层中混合的N的质量分数是~0.01，它们与观测值是一致的。6Li，Be和N在低金属丰度的进一步观察应该为我们提供这种生产方案的关键测试。
We investigate energetic Type Ic supernovae as production sites for 6Li and Be in the early stages of the Milky Way. Recent observations have revealed that some very metal-poor stars with [Fe/H] < -2.5 possess unexpectedly high abundances of 6Li. Some also exhibit enhanced abundances of Be as well as N. From a theoretical point of view, recent studies of the evolution of metal-poor massive stars show that rotation-induced mixing can enrich the outer H and He layers with C, N, and O (CNO) elements, particularly N, and at the same time cause the intense mass loss of these layers. Here we consider energetic supernova explosions occurring after the progenitor star has lost all but a small fraction of the He layer. The fastest portion of the supernova ejecta and the circumstellar matter (CSM), both of which are composed of He and CNO, can interact directly and induce light-element production through spallation and He-He fusion reactions. The CSM should be sufficiently thick to energetic particles so that the interactions terminate within its innermost regions. We calculate the resulting 6Li/O and 9Be/O ratios in the ejecta + CSM material out of which the very metal-poor stars may form. We find that they are consistent with the observed values if the mass of the He layer remaining on the preexplosion core is ~0.01-0.1 M☉ and if the mass fraction of N mixed in the He layer is ~0.01. Further observations of 6Li, Be, and N at low metallicity should provide us with critical tests of this production scenario.