Stochastic Chemical Evolution of Radioactive Isotopes with a Monte Carlo Approach
Stochastic Chemical Evolution of Radioactive Isotopes with a Monte Carlo Approach
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用蒙特卡罗方法研究放射性同位素的随机化学演化
DOI：
10.3847/1538-4357/ab5a88
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
M. Lugaro
中科院分区：
文献类型：
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作者：
B. Cot'e;A. Yagüe;Blanka Világos;M. Lugaro
平均寿命τ为几百万年到几百万年的短寿命放射性核素（SLR）为探测星际介质中最近的核合成事件和太阳形成的物理条件提供了独特的机会。在这里，我们量化的不确定性，在一个包裹的星际气体的恒星富集事件的随机性质的预测演变的SLR。我们假设在每个时间间隔γ处形成富集祖细胞。对于每个祖先，我们随机采样的延迟时间之间的形成和富集事件，基于几个延迟时间分布（DTD）的功能，涵盖了广泛的天体物理学网站。对于每一组τ、γ和DTD函数，我们遵循15 Gyr的SLR丰度，并重复此过程数千次，以推导出它们的概率分布。对于τ/γ τ 2，分布取决于DTD函数，我们提供了列表值和解析表达式来量化扩散。当τ/γ = 1时，相对丰度不确定度最大可达60%。对于τ/γ <$1，我们给出了SLR丰度只携带一个富集事件的概率，当τ/γ <$0.3时，该概率大于50%。对于0.3 π τ/γ π 2，少数事件对SLR丰度有贡献。这种情况需要用单独的统计方法进行调查。我们发现，太阳诞生的时间大约为900 - 1300万年，与早期太阳系中观测到的60 Fe，107 Pd和182 Hf的丰度一致，假设这些同位素的τ/γ为3。
Short-lived radionuclides (SLRs) with mean lives τ of a few to hundreds of Myr provide unique opportunities to probe recent nucleosynthesis events in the interstellar medium and the physical conditions in which the Sun formed. Here we quantify the uncertainty in the predicted evolution of SLRs within a parcel of interstellar gas given the stochastic nature of stellar enrichment events. We assume that an enrichment progenitor is formed at every time interval γ. For each progenitor, we randomly sample the delay time between its formation and its enrichment event, based on several delay-time distribution (DTD) functions that cover a wide range of astrophysical sites. For each set of τ, γ, and DTD functions, we follow the abundances of SLRs for 15 Gyr and repeat this process thousands of times to derive their probability distributions. For τ/γ ≳ 2, the distributions depend on the DTD function, and we provide tabulated values and analytical expressions to quantify the spread. The relative abundance uncertainty reaches a maximum of ∼60% for τ/γ = 1. For τ/γ ≲ 1, we provide the probability for the SLR abundance to carry the signature of only one enrichment event, which is greater than 50% when τ/γ ≲ 0.3. For 0.3 ≲ τ/γ ≲ 2, a small number of events contributed to the SLR abundance. This case needs to be investigated with a separate statistical method. We find that an isolation time for the birth of the Sun of roughly 9–13 Myr is consistent with the observed abundances of 60Fe, 107Pd, and 182Hf in the early solar system when assuming τ/γ ∼ 3 for these isotopes.