第一代恒星的锶与钡产额：来自贫金属星的约束
Sr and Ba yields of the First Generation(s) of stars: Constraints from metal-poor stars
浏览论文内容
中文总结 AI 辅助
本研究分析10颗极端贫金属星，识别4个[Sr/Ba]组，利用锶产额揭示SASS恒星由约1-10个前身事件增丰形成，其锶丰度分散源于核合成产额变化，为早期超新星核合成研究提供约束。
中文摘要 AI 辅助
我们基于高分辨率（R≈28000）的麦哲伦望远镜/MIKE光谱，对10颗新发现的极端贫金属星开展化学丰度分析，其金属丰度范围为-4.05≤[Fe/H]≤-2.33。其中8颗恒星的重元素丰度较低，[Sr/H]<-4.5且[Ba/H]<-4.0，属于小吸积恒星系统（SASS）恒星；另有4颗属于超中子俘获元素贫星，[Sr/H]<-5.0，包括Gaia DR3 5729400267359655680，其[Sr/H]=-6.4，创下已探测到的最低锶丰度新纪录。我们在更广泛的SASS恒星群体中识别出4个不同的[Sr/Ba]组，其范围从[Sr/Ba]=-2.0到+1.6，表明存在多种前身天体事件及不同的核合成过程/场所。为探究该[Sr/Ba]大范围的起源，我们为这4个组采用与场所无关的锶产额，分别为[Sr/H]=-6、-5.75、-5.42和-4.93。应用这些产额表明，大多数SASS恒星形成于被约1-10个前身天体事件增丰的气体，与其极端贫金属的性质预期一致。因此，我们将[Sr/H]丰度的分散归因于每个核合成场所/事件的锶产额内在变化。我们为每个[Sr/Ba]组提出的锶产额及相关核合成起源是合理且具有代表性的近似，误差在几倍以内，可约束未来早期核心坍缩超新星的重元素核合成理论计算。
英文摘要
We present our chemical abundance analysis of ten new extremely metal-poor stars with $-4.05\leq\mbox{[Fe/H]}\leq-2.33$, based on high-resolution (R $\sim28,000$) Magellan/MIKE spectra. Eight of our stars have low heavy-element abundances of $\mbox{[Sr/H]}<-4.5$ and $\mbox{[Ba/H]}<-4.0$, making them Small Accreted Stellar System (SASS) stars. Four are hyper neutron-capture-element poor with $\mbox{[Sr/H]}<-5.0$, including Gaia DR3 5729400267359655680, which sets a new record for the lowest detected Sr abundance of $\mbox{[Sr/H]} =-6.4$. We identify four distinct [Sr/Ba] groups within the wider SASS star population which span a large range from $\mbox{[Sr/Ba]} =-2.0$ to +1.6, pointing to multiple types of progenitor events and different nucleosynthesis processes/sites. To explore the origins of this large [Sr/Ba] range, we adopt site-agnostic Sr yields of $\mbox{[Sr/H]}=-6$, $-5.75$, $-5.42$, and $-4.93$ for the four groups. Applying those yields suggests that the majority of SASS stars formed from gas enriched by $\sim$1-10 progenitor events, consistent with expectations from their extremely metal-poor nature. We thus attribute the [Sr/H] abundance scatter to intrinsic variations in the Sr yield per nucleosynthesis site/event. Our proposed Sr yields for each [Sr/Ba] group and associated nucleosynthesis origin are a reasonable and representative approximation, good to within a factor of a few, and can constrain future theoretical heavy element nucleosynthesis calculations in early core-collapse supernovae.
