Collaborative Research: Empirical Constraints on the s- and r-processes from Precision Nebular Abundances

比铁峰元素重的元素的起源是现代天体物理学中的一个重要问题。本研究项目的目标是更好地定义慢（s-）和快（r-）中子(n)捕获过程对宇宙中反式铁元素丰度的相对贡献，这两个过程分别发生在垂死的类太阳恒星和中子星合并中。为了实现这一目标，研究人员将在银河系和麦哲伦星云的行星状星云（PNe）的不同样本中测量六种n捕获元素（Se, Br, Rb, Te， Xe和Kr）离子的红外光谱和光学光谱。他们的分析将揭示准确的丰度，反映恒星在成为行星状星云之前产生的每种元素的数量。该项目的结果将促进天文学家对核合成和星系化学演化的理解。该项目将为本科生提供真实的研究经验，并支持一个充满活力的高中生科学推广计划。使用每种元素的多个离子，研究人员将获得元素丰度，相对于以前的测定精度要高得多。稳健的丰度测定将在渐近巨支（AGB）恒星中获得可靠的s过程元素富集因子，这些恒星是PNe的祖先和恒星群中主要的s过程位点。量化s-过程对PNe的贡献，跨越广泛的前体质量和金属丰度，将使研究人员能够对r-过程对这些元素及其候选位点的贡献范围施加严格的经验约束。这也将使他们能够区分AGB恒星的不同进化和核合成模型。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The origin of elements heavier than the iron-peak elements is an important question in modern astrophysics. The goal of this research project is to better define the relative contributions of the slow (s-) and rapid (r-) neutron(n)-capture processes, which occur respectively in dying Sun-like stars and in mergers of neutron stars, to the cosmic abundances of the trans-iron elements. To achieve that goal, the investigators will measure infrared and optical spectra of the ions of six n-capture elements (Se, Br, Rb, Te, Xe, and Kr) in a diverse sample of planetary nebulae (PNe) in the Milky Way and the Magellanic Clouds. Their analyses will reveal accurate abundances that reflect the amount of each element produced in the star before it became a planetary nebula. Results from the project will advance astronomers’ understanding of nucleosynthesis and galactic chemical evolution. This project will provide authentic research experiences to undergraduate students and support a vibrant program of science outreach to high school students.Using multiple ions of each element, the investigators will derive elemental abundances with far higher precision relative to previous determinations. The robust abundance determinations will yield reliable s-process elemental enrichment factors in Asymptotic Giant Branch (AGB) stars, which are the progenitors of PNe and major s-process sites in stellar populations. Quantifying the s-process contributions in PNe spanning a wide range in progenitor mass and metallicity will allow the investigators to place stringent empirical constraints on the range of r-process contributions to these elements and their candidate sites. It will also allow them to distinguish between different sets of evolutionary and nucleosynthetic models for AGB stars.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.