K矮星和毕星团中的铁异常
On the Iron Abundance Anomaly in K-dwarf and Hyades Stars
摘要：
使用标准的1D-LTE模型大气分析，我们提供了一个深入的调查铁丰度来自中性和单电离铁线（Fe { \scriptsize{I, II} }）在附近的星团。具体来说，我们复制了关于$Δ$ [Fe/H]的差异，其中Fe { \scriptsize{II} } - Fe { \scriptsize{I} }的差异随着$T_\mathrm{eff}$的降低而增加，在$T_\mathrm{eff}$ $\thicksim$ 4000 K时达到惊人的1.0 dex。以前的研究已经调查了昴星团和毕星团中的这种异常，但没有具体的解决方案。在这项分析中，我们探测了两个样本：63颗宽视场双星，其中主星的温度与太阳相似，而主星是K矮星，温度范围从4231 K $\leq$ $T_\mathrm{eff}$ 6453 K，33颗毕宿星的温度为4268 K $\leq$ $T_\mathrm{eff}$ $\leq$ 6072 K。以前的研究发现了1.0 dex数量级的差异。然而，我们发现这些研究忽略了某些Fe { \scriptsize{II} }线的线混合效应，即$λ$ = \{4508.29 Å，4993.34 Å，5197.58 Å，5325.55 Å，5425.26 Å，6456.38 Å\}。当这些谱线从谱线列表中删除后，我们发现$Δ$ [Fe/H]在场双星中降低到$\thicksim$ 0.6 dex，在毕宿星中降低到$\thicksim$ 0.3 dex。通过探测NLTE效应以及使用Ca { \scriptsize{II} } H+K发射和Li吸收的年龄和活动考虑来研究这种剩余趋势的原因，但这些结果似乎很小甚至可以忽略不计。
英文摘要：
Using standard 1D-LTE model atmosphere analysis, we provide an in-depth investigation of iron abundance as derived from neutral and singly ionization iron lines (Fe {\scriptsize{I, II}}) in nearby star clusters. Specifically, we replicate the discrepancy regarding $Δ$[Fe/H], wherein the difference of Fe {\scriptsize{II}} - Fe {\scriptsize{I}} increases for stars of the same cluster with decreasing $T_\mathrm{eff}$, reaching an astonishing 1.0 dex at $T_\mathrm{eff}$ $\thicksim$ 4000 K. Previous studies have investigated this anomaly in the Pleiades and Hyades clusters with no concrete solution. In this analysis, we probe two samples: 63 wide binary field stars where the primary star is of sun-like temperatures and the secondary is a K-dwarf, ranging from 4231 K $\leq$ $T_\mathrm{eff}$ $\leq$ 6453 K, and 33 Hyades stars of temperatures 4268 K $\leq$ $T_\mathrm{eff}$ $\leq$ 6072 K. Previous studies have found discrepancies on the order of 1.0 dex. However, we find that these studies have neglected line-blending effects of certain Fe {\scriptsize{II}} lines, namely $λ$ = \{4508.29 Å, 4993.34 Å, 5197.58 Å, 5325.55 Å, 5425.26 Å, 6456.38 Å\}. When these lines are removed from the line-list, we find $Δ$[Fe/H] decreases to $\thicksim$ 0.6 dex in the field binaries and $\thicksim$ 0.3 dex in the Hyades. The reason for this remaining trend is investigated by probing NLTE effects, as well as age and activity considerations using Ca {\scriptsize{II}} H+K emission and Li absorption, but these results appear to be small to negligible.
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