WIYN open cluster study: The old open cluster, NGC 188, and a re-evaluation of Lithium-richness among red giants
WIYN open cluster study: The old open cluster, NGC 188, and a re-evaluation of Lithium-richness among red giants
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WIYN 疏散星团研究：古老的疏散星团 NGC 188 以及红巨星中锂丰富度的重新评估
DOI：
10.1093/mnras/stac1251
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发表时间：
2022
影响因子：
4.8
通讯作者：
Steinhauer, Aaron
中科院分区：
文献类型：
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作者：
Sun, Qinghui;Deliyannis, Constantine P.;Twarog, Bruce A.;Anthony-Twarog, Barbara J.;Cummings, Jeffrey D.;Steinhauer, Aaron
我们给出了NGC 188的34个红巨星候选成员的WIYN/Hydra光谱，连同WOCS和Gaiplane，得到了23个单成员，6个二元成员，4个单非成员和1个二元非成员。我们报道了29个成员的[Fe/H]，并推导出[Fe/H] NGC 188 = +0.064 ± 0.018dex（σμ）（天谱产额A（Fe）= 7.520 ± 0.015dex（σμ））。我们讨论了不同的Yale-Yonsei等时线的导出参数，以适应关闭的影响。我们利用温度最低、重力最低的巨星来完善Li 6707.8 <$m附近的谱线列表。通过综合，我们分别得到了4346、4705、5027和6353恒星的A（Li）= 1.17、1.65、2.04和0.60 dex，以及其他成员的3σ上限。虽然只有两个探测到符合A（Li）> 1.5 dex的“Li丰度”的传统标准，但我们认为，由于星团A（Li）随着亚巨星演化到RGB的底部而消失，因此所有四颗恒星在该星团的背景下都富含Li。在29颗恒星的样本中，即使只有几颗富锂恒星的出现率也远远高于最近在该领域进行的大型调查。所有四颗恒星都位于稍微或实质上远离星团基准序列的地方，可能提供了关于它们锂丰度的线索。我们讨论了一些可能性的起源为李在每个星星，并建议潜在的歧视未来的意见。
We present WIYN/Hydra spectra of 34 red giant candidate members of NGC 188, which, together with WOCS andGaiadata yield 23 single members, 6 binary members, 4 single non-members, and 1 binary non-member. We report [Fe/H] for 29 members and derive [Fe/H]NGC188= +0.064 ± 0.018 dex (σμ) (sky spectra yield A(Fe)⊙= 7.520 ± 0.015 dex (σμ)). We discuss effects on the derived parameters of varying Yale-Yonsei isochrones to fit the turnoff. We take advantage of the coolest, lowest gravity giants to refine the line list near Li 6707.8 Å. Using synthesis we derive detections of A(Li) = 1.17, 1.65, 2.04, and 0.60 dex for stars 4346, 4705, 5027, and 6353, respectively, and 3σ upper limits for the other members. Whereas only two of the detections meet the traditional criterion for ‘Li-richness’ of A(Li) > 1.5 dex, we argue that since the cluster A(Li) vanish as subgiants evolve to the base of the RGB, all four stars are Li-rich in this cluster’s context. An incidence of even a few Li-rich stars in a sample of 29 stars is far higher than what recent large surveys have found in the field. All four stars lie either slightly or substantially away from the cluster fiducial sequence, possibly providing clues about their Li-richness. We discuss a number of possibilities for the origin for the Li in each star, and suggest potentially discriminating future observations.