标题： 钡同位素比值在贫金属恒星中的研究：用球状星团校准该方法 显示英文标题

标题： Barium isotopic ratios in metal-poor stars: calibrating the method with globular clusters

摘要： 确定重元素在恒星大气中富集的核合成过程是具有挑战性的。 它通常依赖于将观测到的丰度与铁的比值与相对于太阳的理论预测进行比较，但这种方法由于经典一维静力模型的局限性而容易产生不确定性。 一种有前景但仍研究不足的方法是通过聚焦于同时受到慢速（s）过程和快速（r）过程贡献的元素，来测量恒星大气的同位素组成。 虽然研究总元素丰度提供了一个简化的视图，但同位素比值直接与底层的核合成过程相关。 我们的目标是提供一种可靠的方法，用于量化s过程和r过程对恒星大气中钡的贡献。 这是通过结合1D大气模型和经过仔细校准的微湍流，利用次线和共振Ba线之间的比较来确定钡的同位素比值实现的。 在本初步研究中，我们使用球状星团NGC 6752的成员恒星来校准微湍流（$v_{mic}$）值，适用于不同恒星演化阶段的次线和共振钡线。 这使我们能够提供一个可靠的 $v_{mic}$估计值，该值可用于准确确定从主序星到上红巨星分支的恒星中的钡丰度和同位素比值。 为钡次线适应的 $v_{mic}$量表与从3D模型大气得出的量表一致，因此后来的 $T_{\mathrm{eff}}$-log $g$依赖关系可以安全使用。 共振线在 $\lambda$4934埃的 $v_{mic}$用于同位素比值的确定更高，并且依赖于等效宽度（EW）。 我们提供$v_{mic}$与 EW 之间的校准关系，用于测量同位素比。 显示英文摘要

摘要： Identifying the nucleosynthesis processes behind heavy-element enrichment in stellar atmospheres is challenging. It typically relies on comparing observed abundance-to-iron ratios with theoretical predictions relative to the Sun, but this method is prone to uncertainty due to limitations of classical 1D hydrostatic models. One promising but still underexplored approach is to measure the isotopic composition of stellar atmospheres by focusing on elements that have both slow (s)-process and rapid (r)-process contributions. While the study of total elemental abundances offers a simplified view, isotopic ratios are directly linked to the underlying nucleosynthesis processes. Our aim is to provide a reliable method for quantifying the contributions of the s- and r-processes to barium in stellar atmospheres. This is achieved by determining barium isotopic ratios using 1D atmospheric models in combination with a carefully calibrated microturbulence, based on the comparison between subordinate and resonance Ba lines. In this initial study, we use member stars of the globular cluster NGC 6752 to calibrate the microturbulence ($v_{mic}$) value for both subordinate and resonance barium lines across different stellar evolutionary stages. This allows us to provide a reliable estimate of $v_{mic}$ that can be applied to accurately determine barium abundances and isotopic ratios in stars ranging from the main sequence to the upper red giant branch. The $v_{mic}$ scale adapted for barium subordinate lines is consistent with that derived from 3D model atmospheres, and thus the $T_{\mathrm{eff}}$-log $g$ dependent relations of the later can be used safely. The $v_{mic}$ for the resonance line at $\lambda$4934 Angstrom -- for the determination of the isotopic ratio -- is higher, and depends on the equivalent width (EW). We provide calibrated relations between $v_{mic}$ and EW for measuring isotopic ratios.