Nucleosynthesis in Magnetically Driven Jets from Collapsars
Nucleosynthesis in Magnetically Driven Jets from Collapsars
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DOI：
10.1086/529416
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发表时间：
2008-04
期刊：
影响因子：
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通讯作者：
Shin-ichiro Fujimoto;N. Nishimura;M. Hashimoto
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文献类型：
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作者：
Shin-ichiro Fujimoto;N. Nishimura;M. Hashimoto
我们已经做了详细的计算，磁驱动喷流喷出的组成，从恒星，或快速旋转的大质量恒星，基于长期的磁流体动力学模拟的核心崩溃与各种分布的磁场和角动量的崩溃前。我们遵循的演化约4000种核素的丰度从崩溃阶段的喷射阶段，并通过射流生成阶段使用一个大型的核反应网络。我们发现，r-过程成功地运作，只有在高能喷流（>1051尔格），这样的U和Th的合成丰富，即使在磁星有一个相对较弱的磁场（1010 G）和适度旋转的核心崩溃前。喷流内部的丰度模式与太阳系中r元素的丰度模式相似。大约0.01-0.06 M的富中子重核以高能喷流的形式从一颗恒星中喷射出来。较高能量的喷流含有大量的56 Ni，从3.7 × 10−4到0.06 M不等。能量较低的喷流，喷射出少量的56镍，可以在没有超新星的情况下诱发伽马射线暴（GRB），例如GRB 060505或GRB 060614。如果伽玛暴和超新星都是由黑洞附近的喷流引起的，那么相当数量的r-元素很可能从伽玛暴和超新星中喷出。
We have made detailed calculations of the composition of magnetically driven jets ejected from collapsars, or rapidly rotating massive stars, based on long-term magnetohydrodynamic simulations of their core collapse with various distributions of magnetic field and angular momentum before collapse. We follow the evolution of the abundances of about 4000 nuclides from the collapse phase to the ejection phase and through the jet generation phase using a large nuclear reaction network. We find that the r-process successfully operates only in energetic jets (>1051 ergs), such that U and Th are synthesized abundantly, even when the collapsar has a relatively weak magnetic field (1010 G) and a moderately rotating core before the collapse. The abundance patterns inside the jets are similar to those of the r-elements in the solar system. About 0.01-0.06 M☉ of neutron-rich, heavy nuclei are ejected from a collapsar with energetic jets. The higher energy jets have larger amounts of 56Ni, varying from 3.7 × 10−4 to 0.06 M☉. Less energetic jets, which eject small amounts of 56Ni, could induce a gamma-ray burst (GRB) without a supernova, such as GRB 060505 or GRB 060614. Considerable amounts of r-elements are likely to be ejected from GRBs with hypernovae, if both the GRB and hypernova are induced by jets that are driven near the black hole.