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arXiv 2408.12971astro-ph.GAastro-ph.SR
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M巨星与IGRINS IV：s元素钡的一条近红外谱线的识别与表征

M giants with IGRINS IV. Identification and characterization of a near-IR line of the s-element Barium

G. Nandakumar, N. Ryde, H. Hartman, G. Mace

备注：
9 pages, 6 figures, Accepted for publication A&A
发表信息：
A&A 690, A226 (2024)
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AI总结：

本研究利用IGRINS光谱仪观测太阳附近37颗M巨星的近红外光谱，识别并表征了K波段2.33 μm处的钡谱线，证明其适用于M巨星丰度分析，为研究受尘埃遮蔽族群的核合成通道提供了新途径。

摘要：

中子俘获元素代表了恒星族群银河系化学演化研究中的一个重要核合成通道。对于受到严重消光影响的恒星族群，例如位于银河系中心和银道面方向的族群，基于近红外光谱的丰度分析是必要的。此前，中子俘获元素如铜、铈、钕和镱的谱线已在H波段被识别，而钇的谱线已在K波段被识别。由于近红外波段中子俘获元素谱线稀缺，增加来自其他中子俘获元素的有用谱线是非常理想的。本工作旨在识别并表征一条适合丰度测定的谱线，该谱线来自最常用的s过程元素，即钡。我们使用GEMINI South望远镜上的IGRINS光谱仪，观测了太阳附近37颗M巨星的高信噪比、高分辨率近红外光谱。使用手动光谱合成方法，我们确定了这些恒星的恒星参数，并从K波段波长λ_air=23253.56 Å处的Ba线（6s5d ^3D_2 → 6s6p ^3P^o_2）导出了钡丰度。我们证明K波段2.33 μm（λ23253.56）处的Ba线适用于M巨星光谱的丰度分析。该谱线在较高温度下逐渐变弱，仅在超太阳金属丰度的M巨星和最冷K巨星中才有用。我们现在可以将Ba加入到可从高分辨率H波段和K波段光谱中提取的重元素Cu、Zn、Y、Ce、Nd和Yb的趋势中。这开启了对受尘埃遮蔽族群（如银河系中心）中核合成通道（包括s过程和r过程）的研究。

英文摘要：

Neutron-capture elements represent an important nucleosynthetic channel in the study of the Galactic Chemical Evolution of stellar populations. For stellar populations behind significant extinction, such as those in the Galactic Center and along the Galactic plane, abundance analyses based on near-IR spectra are necessary. Previously, spectral lines from the neutron-capture elements such as copper (Cu), cerium (Ce), neodymium (Nd), and ytterbium (Yb) have been identified in the H band, while yttrium (Y) lines have been identified in the K band. Due to the scarcity of spectral lines from neutron-capture elements in the near-IR, the addition of useful spectral lines from other neutron-capture elements is highly desirable. The aim of this work is to identify and characterise a spectral line suitable for abundance determination from the most commonly used s-process element, namely barium. We observed near-IR spectra of 37 M giants in the solar neighbourhood at high S/N and high spectral resolution using the IGRINS spectrometer on the GEMINI South telescope. Using a manual spectral synthesis method, we determined the stellar parameters for these stars and derived the barium abundance from the Ba line (6s5d $^3$D$_2 \rightarrow$ 6s6p $^3$P$^o_2$) at $λ_\mathrm{air}=23\,253.56\,$Å in the K band. We demonstrate that the Ba line in the K band at 2.33\,\mic\ ($λ$23253.56) is useful for abundance analysis from spectra of M giants. The line becomes progressively weaker at higher temperatures and is only useful in M giants and the coolest K giants at supersolar metallicities. We can now add Ba to the trends of the heavy elements Cu, Zn, Y, Ce, Nd, and Yb, which can be retrieved from high-resolution H- and K-band spectra. This opens up the study of nucleosynthetic channels, including the s-process and the r-process, in dust-obscured populations such as the Galactic Center.

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