论文标题
盖亚香肠和红杉的R-Process富集升高
Elevated r-process enrichment in Gaia Sausage and Sequoia
论文作者
论文摘要
Gaia香肠（GS）和红杉代表了构成银河系恒星光环的主要积聚事件。对这些主要构建基块的详细化学研究提供了对银河组装的早期步骤的原始视图。我们介绍了使用GAIA DR2进行运动学选择的82m VLT VLT的尺寸高分辨率光谱观测的分析结果。我们使用Nissen＆Schuster（2011）和Galah DR3（2020）的档案数据进行了一组测量。在这里，我们通过分析SR，Y，BA和欧盟行为来关注中子捕获过程。我们检测到欧盟丰度的明显增强（[EU/Fe] 〜0.6-0.7），指示R-Process在恒星N捕获化妆中的大量流行率。我们还能够追溯到在多种金属性范围内产生重元素的演变。钡到Europium从[Ba/eu] = -0.7的紧密平坦序列变化，反映了从爆炸巨大的恒星造成的主要贡献，转变为在较高的铁丰度下的明显上流，背叛了渐近巨型巨型分支（AGB）射出的污染发作。此外，我们在[Fe/H] - [BA/Fe]平面中发现了两个明确的序列，这可能是由于GS祖细胞内的S过程污染和混合的不同水平引起的。
The Gaia Sausage (GS) and the Sequoia represent the major accretion events that formed the stellar halo of the Milky Way. A detailed chemical study of these main building blocks provides a pristine view of the early steps of the Galaxy's assembly. We present the results of the analysis of the UVES high-resolution spectroscopic observations at the 8.2m VLT of 9 Sausage/Sequoia members selected kinematically using Gaia DR2. We season this set of measurements with archival data from Nissen & Schuster (2011) and GALAH DR3 (2020). Here, we focus on the neutron-capture process by analysing Sr, Y, Ba and Eu behavior. We detect clear enhancement in Eu abundance ([Eu/Fe]~0.6-0.7) indicative of large prevalence of r-process in the stellar n-capture makeup. We are also able to trace the evolution of the heavy element production across a wide range of metallicity. The barium to europium changes from a tight, flat sequence with [Ba/Eu]=-0.7 reflecting dominant contribution from exploding massive stars, to a clear upturn at higher iron abundances, betraying the onset of contamination from asymptotic giant branch (AGB) ejecta. Additionally, we discover two clear sequences in [Fe/H]-[Ba/Fe] plane likely caused by distinct levels of s-process pollution and mixing within the GS progenitor.
