发表机构
University of Cambridge; Northwestern University; New Mexico State University; Carnegie Institution for Science; Australian National University; Stockholm University; University College London（剑桥大学; 西北大学; 新墨西哥州立大学; 卡内基科学促进会; 澳大利亚国立大学; 斯德哥尔摩大学; 伦敦大学学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究在GALAH巡天中发现17颗银盘富Eu恒星，其中14颗为r-II星，并提出了适用于银盘的新Eu增强选择标准，为高金属丰度下r过程研究提供了宝贵示踪体。
AI 中文摘要
富含铕（Eu）等重中子俘获元素的恒星为了解最稀有、最奇特的核合成事件提供了窗口。迄今发现的大多数富Eu恒星都存在于贫金属星族中，其金属丰度为$\mathrm{[Fe/H]}<-1.0$。在此，我们报告在GALAH巡天观测的74,717颗恒星中，发现了17颗经过验证的富Eu恒星（$\mathrm{[Eu/Fe]}>0.7$），它们位于银盘，金属丰度范围在$-0.87<\mathrm{[Fe/H]}<-0.21$之间。其中14颗恒星还具有$\mathrm{[Ba/Eu]}<0$的特征，标志着快速中子俘获（$r$）过程的增强，使其成为r-II恒星。在这些恒星中，有一颗恒星在$\mathrm{[Fe/H]}=-0.21$时具有异常高的$\mathrm{[Eu/H]}=1.01\pm0.09$。除Eu外，所有17颗恒星在其他中子俘获元素（尤其是Nd）上也表现出增强，而在其他方面，其化学组成与典型盘星一致，特别是在其$\alpha$元素丰度上。其中两颗富Eu恒星显示出双星迹象，且Ba和Y含量显著增强，标志着慢速或中速中子俘获过程的潜在特征。这17颗富Eu恒星样本跨越了高$\alpha$和低$\alpha$银盘，是高金属丰度下中子俘获过程（包括$r$过程）的宝贵示踪体。尽管我们使用了通常应用于银晕的富Eu恒星标准，以便与文献中关于$r$过程增强恒星的研究进行比较，但我们提出了一种新的、依赖金属丰度的Eu增强选择标准，该标准更适合银盘区域。
英文摘要
Stars enhanced in heavy neutron capture elements like europium (Eu) provide a window into the rarest and most exotic nucleosynthetic events. Most Eu-enhanced stars discovered thus far are found among metal-poor populations, with $\mathrm{[Fe/H]}<-1.0$. Here, we report the discovery of $17$ vetted Eu-enhanced stars ($\mathrm{[Eu/Fe]}>0.7$) in the Milky Way disk with metallicities in the range $-0.87<\mathrm{[Fe/H]}<-0.21$ identified from among $74\,717$ stars in the GALAH survey. 14 of these stars additionally have $\mathrm{[Ba/Eu]}<0$, marking enhancement from the rapid neutron capture ($r$-) process and making these r-II stars. Included in their number is a star with a remarkably high $\mathrm{[Eu/H]}=1.01\pm0.09$ at $\mathrm{[Fe/H]}=-0.21$. In addition to Eu, all 17 stars show enhancements in other neutron capture elements, especially in Nd, while otherwise appearing chemically consistent with typical disk stars, particularly in their $α$-element abundances. Two of the Eu-enhanced stars exhibit indications of binarity with strong enrichment in Ba and Y, marking potential signatures of the slow or intermediate neutron capture processes. This sample of 17 Eu-enhanced stars, which span both the high- and low-$α$ disks, are valuable tracers of neutron capture processes, including the $r$-process, at high metallicities. Although we use criteria for Eu-enhanced stars typically applied to the halo to enable comparison to literature studies of $r$-process enhanced stars, we propose a new, metallicity-dependent selection for Eu enhancement that is better-suited to the regime of the Galactic disk.
CommentsSubmitted to MNRAS. 16 pages, 9 figures, 2 tables in the appendices. Alt text included for figures. Comments very welcome!
