AI 中文总结
研究通过IGRINS观测12个麦哲伦云行星状星云，检测到多种s-过程元素，对比三类AGB模型发现部分模型匹配度较好，为恒星演化及星系化学演化建模提供关键数据。
AI 中文摘要
我们呈现了利用双子座南望远镜上的高分辨率近红外光谱仪IGRINS获取的12个麦哲伦云行星状星云（PNe）的观测结果。在10个目标中，我们检测到多个中子（n）俘获元素，这些元素是在先前的渐近巨星支（AGB）阶段通过s-过程合成的，包括广泛观测到的硒（Se）和氪（Kr），以及河外行星状星云中首次检测到的铷（Rb）、镉（Cd）和碲（Te）。推导得出的丰度显著扩展了亚太阳金属度恒星群中行星状星云的铁族元素丰度测定清单。7个目标相对于金属度参考元素氧（O）和氩（Ar）表现出s-过程富集，其中碲和氪的丰度提升倍数高达约40至50倍。我们将这些结果与AGB核合成预测进行了比较，使用机器学习算法寻找最匹配的Monash、FRUITY和NuGrid模型。对于其中5个行星状星云，质量为2至4倍太阳质量、金属度从1/3太阳到近太阳的Monash和FRUITY模型与观测结果匹配良好，尽管Monash模型更成功地拟合了最大的氪增强。NuGrid模型预测的s-过程富集程度小于观测值，但可用模型数量有限，难以评估其再现观测丰度的能力。我们未能找到能很好拟合另外3个富集行星状星云的模型，包括样本中金属最贫乏的天体。这些比较解决了低质量和中等质量恒星晚期演化过程中质量损失、对流和其他混合机制的不确定性，并提高了AGB恒星s-过程产额的准确性，而这些是星系化学演化建模的关键参数。
英文摘要
We present observations of 12 Magellanic Cloud planetary nebulae (PNe) obtained with the high-resolution near-infrared spectrometer IGRINS on Gemini South. In 10 targets we detect multiple neutron(n)-capture elements that can be synthesized by the s-process during the preceding asymptotic giant branch (AGB) phase, including the widely-observed species Se and Kr, and first detections of Rb, Cd, and Te in extragalactic PNe. The derived abundances significantly expand the inventory of trans-iron element abundance determinations from PNe in subsolar metallicity stellar populations. Seven targets exhibit s-process enrichments relative to the metallicity references O and Ar, with abundances elevated by factors of up to ~40-50 for Te and Kr. We compare these results with AGB nucleosynthesis predictions, using a machine-learning algorithm to find the best-fitting Monash, FRUITY, and NuGrid models. For five of the PNe, Monash and FRUITY models with 2-4 solar masses and metallicities from 1/3 solar to near-solar match the observations well, although the Monash models more successfully fit the largest Kr enhancements. NuGrid models predict smaller s-process enrichments than observed, but the limited number of available models makes it difficult to assess their ability to reproduce the observed abundances. We were unable to find models that provide good fits to three other enriched PNe, including the most metal-poor objects in our sample. These comparisons address uncertainties in mass loss, convection, and other mixing mechanisms during the late evolution of low- and intermediate-mass stars, and improve the accuracy of s-process yields of AGB stars, which are key parameters for modeling galactic chemical evolution.
Comments39 pages, 15 figures, accepted for publication in ApJS
