The long-term evolution of neutron star merger remnants – I. The impact of r-process nucleosynthesis
The long-term evolution of neutron star merger remnants – I. The impact of r-process nucleosynthesis
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DOI：
10.1093/mnras/stt2502
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发表时间：
2013-07
影响因子：
4.8
通讯作者：
S. Rosswog;O. Korobkin;A. Arcones;F. Thielemann;T. University;Okc;I. Darmstadt;U. Basel;R. I. O. Physics
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文献类型：
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作者：
S. Rosswog;O. Korobkin;A. Arcones;F. Thielemann;T. University;Okc;I. Darmstadt;U. Basel;R. I. O. Physics
我们跟踪中子星星合并的动态喷出物的长期演化，时间长达100年，密度范围约为40个数量级。我们包括从新鲜合成的，放射性衰变的原子核在我们的模拟和研究其对残余动力学的影响的核能输入。虽然核加热大大改变了长期的演变，我们发现，运行核网络在纯流体动力学模拟（即没有加热）产生实际上可以接受的核合成结果。辐射加热的主要动力学效应是迅速消除初始质量分布的不均匀性，随后演化自相似地进行，100年后残余物仍然携带着初始二元质量比的记忆。我们还探讨了两个质量喷射通道的核合成产额。动态喷出物非常稳健地产生A > 130的“强”r过程元素，其模式基本上与合并系统的细节无关。从一个简单的模型，我们发现中微子驱动的风产生'弱'的r-过程的贡献与50 < A < 130，其丰度模式在不同的合并情况下变化很大。这是因为它们的电子分数，由中微子光度的比例决定，在不同的情况下变化很大。这样的风不会产生任何Ni-56，但会产生一系列放射性同位素，这些同位素的寿命足够长，除了动态喷出物中的“macronova”之外，还会产生第二个放射性供电的电磁瞬变。虽然我们的风模型非常简单，但它仍然证明了这种中微子驱动的风对电磁瞬变的潜力，并激发了进一步，更详细的中微子流体动力学研究。在配套文件中更详细地讨论了所提到的瞬态的属性。
We follow the long-term evolution of the dynamic ejecta of neutron star mergers for up to 100 years and over a density range of roughly 40 orders of magnitude. We include the nuclear energy input from the freshly synthesized, radioactively decaying nuclei in our simulations and study its effects on the remnant dynamics. Although the nuclear heating substantially alters the long-term evolution, we find that running nuclear networks over purely hydrodynamic simulations (i.e. without heating) yields actually acceptable nucleosynthesis results. The main dynamic effect of the radioactive heating is to quickly smooth out inhomogeneities in the initial mass distribution, subsequently the evolution proceeds self-similarly and after 100 years the remnant still carries the memory of the initial binary mass ratio. We also explore the nucleosynthetic yields for two mass ejection channels. The dynamic ejecta very robustly produce 'strong' r-process elements with A > 130 with a pattern that is essentially independent of the details of the merging system. From a simple model we find that neutrino-driven winds yield 'weak' r-process contributions with 50 < A < 130 whose abundance patterns vary substantially between different merger cases. This is because their electron fraction, set by the ratio of neutrino luminosities, varies considerably from case to case. Such winds do not produce any Ni-56, but a range of radioactive isotopes that are long-lived enough to produce a second, radioactively powered electromagnetic transient in addition to the 'macronova' from the dynamic ejecta. While our wind model is very simple, it nevertheless demonstrates the potential of such neutrino-driven winds for electromagnetic transients and it motivates further, more detailed neutrino-hydrodynamic studies. The properties of the mentioned transients are discussed in more detail in a companion paper.