R-Process Alliance: unveiling the abundance patterns of ten r-II stars through homogeneous spectral analysis

Old, metal-poor stars can provide unique insights into the rapid neutron capture (r-) process, a key pathway for creating heavy elements. A small subset of these stars shows significant enhancement in r-process elements, making them valuable laboratories for studying the origins and history of these elements.

Building on the discoveries from the R-Process Alliance's initial data release of highly r-process-enhanced stars (r-II) (Hansen et al. (2018), Sakari et al.(2018)), this work presents a detailed chemical analysis of ten such stars. We derive abundances for 38 neutron-capture species covering the full r-process pattern from Sr to U.

I will report on the results from this analysis with a particular focus on two key element regions: the Ru-Ag region, where recent work suggests evidence of fission fragment deposition (Roederer et al. 2023), and the poorly understood third peak elements, Os and Ir.

This work will significantly increase the number of r-II stars with reported Os and Ir abundances in the literature, facilitating a thorough investigation into the behavior of these two elements for the first time. Furthermore, the uniform approach to the abundance analysis used in this work yields the most comprehensive analysis of r-II stars to date, allowing us to investigate star-to-star scatter in the abundances, crucial to comparing against models of nucleosynthesis events.