ABUNDANCES OF RED GIANTS IN OLD OPEN CLUSTERS. V. Be 31, Be 32, Be 39, M 67, NGC 188, AND NGC 1193
ABUNDANCES OF RED GIANTS IN OLD OPEN CLUSTERS. V. Be 31, Be 32, Be 39, M 67, NGC 188, AND NGC 1193
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DOI：
10.1088/0004-6256/139/5/1942
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发表时间：
2010-04
期刊：
影响因子：
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通讯作者：
E. Friel;H. Jacobson;C. Pilachowski
中科院分区：
文献类型：
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作者：
E. Friel;H. Jacobson;C. Pilachowski
基于高分辨率光谱学，我们对旧疏散星团Be 31、Be 32、Be 39、M 67、NGC 188和NGC 1193中的16颗恒星进行了详细的丰度分析。[Fe/H]=−0.30±0.0 2，−0.2 1±0.0 1，+0.0 3±0.0 7，+0.12±0.0 2，−0.22±0.14(S.D.)分别发现了Be 32、Be 39、M 67、NGC 188和NGC 1193。在Be-31视场中观测到的两颗恒星具有不同的径向速度和元素丰度模式，也与Yong等人研究的可能的Be-31星不一致。我们的结论是，这一重要星系团的成员资格尚未确定，因此，这里或之前Be 31研究中测得的任何元素丰度都不应被视为确定的星系团丰度。我们对M67和Be 32星系团的结果与其他研究的结果进行了仔细的比较，结果显示总体上是一致的，并确定了不同分析产生的系统差异。在结合我们的结果和其他研究覆盖整个薄盘RGC范围的团簇的结果之后，我们探索了Fe，O，Na，Mg，Al，Si，Ca，Ti和Ni元素的丰度分布随RGC和年龄的变化。正如在以前的工作中发现的那样，在外盘变平之前，[Fe/H]梯度似乎连续到RGC∼13kpc。对于所考虑的所有元素，[X/Fe]比率在所有RGC处显示0.2-0.3Dex的离散度。所分析的六个星系团的[X/Fe]值与其他金属丰度和银心位置相似的星系团的[X/Fe]值是一致的。我们的整个簇样本显示出[O/Fe]和[Al/Fe]随年龄增加的趋势，尽管这些趋势随着文献中其他簇的加入而消失。更大的、均匀的疏散星团样本是必要的，以验证丰度趋势的存在和大小随年龄的变化。
We present a detailed abundance analysis based on high resolution spectroscopy for 16 stars in the old open clusters Be 31, Be 32, Be 39, M 67, NGC 188, and NGC 1193. Average cluster metallicities of [Fe/H] = −0.30 ± 0.02, −0.21 ± 0.01, +0.03 ± 0.07, +0.12 ± 0.02, and −0.22 ± 0.14 (s.d.) have been found for Be 32, Be 39, M 67, NGC 188, and NGC 1193, respectively. The two stars observed in the field of Be 31 have disparate radial velocities and elemental abundance patterns, and also disagree with the possible Be 31 star studied by Yong et al. We conclude that membership has yet to be established for this important cluster, and therefore no element abundances measured here or in previous studies of Be 31 should be taken as definitive cluster abundances. A careful comparison of our results for the clusters M 67 and Be 32 to those of other studies shows general good agreement and identifies systematic differences resulting from different analyses. After combination of our results with those of other studies for clusters spanning the full Rgc range of the thin disk, we explore the abundance distributions as a function of Rgc and age for the elements Fe, O, Na, Mg, Al, Si, Ca, Ti, and Ni. As found in previous work, the [Fe/H] gradient appears to be continuous up to Rgc ∼ 13 kpc before flattening in the outer disk. [X/Fe] ratios show a scatter of 0.2–0.3 dex at all Rgc, for all elements considered. The [X/Fe] values of the six clusters analyzed here are consistent with those of other clusters of similar metallicity and Galactocentric location. Our whole cluster sample shows trends of increasing [O/Fe] and [Al/Fe] with age, although these trends vanish with the inclusion of other clusters from the literature. Larger, homogeneous open cluster samples are necessary to verify the existence and magnitude of abundance trends with age.