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 8.2 m VLT of nine Sausage/Sequoia members selected kinematically using Gaia DR2. We season this set of measurements with archival data from Nissen & Schuster and GALAH DR3 (2020). Here, we focus on the neutron-capture process by analyzing Sr, Y, Ba, and Eu behavior. We detect clear enhancement in Eu abundance ([Eu/Fe] ∼ 0.6–0.7) indicative of large prevalence of the 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 the [Fe/H]−[Ba/Fe] plane likely caused by distinct levels of s-process pollution and mixing within the GS progenitor.

盖亚香肠（GS）和红杉代表形成银河系恒星光晕的主要吸积事件。对这些主要组成部分的详细化学研究提供了有关银河装配早期步骤的原始视图。我们介绍了使用Gaia DR2在运动学上选择的九个香肠/红杉成员在8.2 m VLT处的UVES高分辨率光谱观察的分析结果。我们使用来自Nissen＆Schuster和GALAH DR3（2020）的档案数据对这组测量值进行调味。在这里，我们通过分析Sr，Y，Ba和Eu行为来关注中子俘获过程。我们检测到明显的Eu丰度增强[[Eu / Fe]〜0.6–0.7），表明恒星n捕获组成中r过程的普遍存在。我们还能够追踪各种金属含量范围内重元素生产的演变。钡到euro的变化从[Ba / Eu] = -0.7的紧密，平坦的序列变化，反映出爆炸的大质量恒星的主要贡献，到铁含量更高时明显呈上升趋势，背离了渐近巨型分支（AGB）喷射的开始。此外，我们发现[Fe / H]-[Ba / Fe]平面中的两个清晰序列可能是由于小号-Process污染和GS祖内的混合。