Beryllium in F and G Field Dwarfs from High-Resolution Canada-France-Hawaii Telescope Spectra
Beryllium in F and G Field Dwarfs from High-Resolution Canada-France-Hawaii Telescope Spectra
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DOI：
10.1086/320949
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发表时间：
2001-06
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影响因子：
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通讯作者：
A. Boesgaard;C. Deliyannis;J. King;A. Stephens
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文献类型：
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作者：
A. Boesgaard;C. Deliyannis;J. King;A. Stephens
为了确定在恒星内部运行的改变轻元素表面组成的机制，在庞大的Li观测库中增加对Be的观测是很重要的。铍比Li更能抵抗破坏，所以关于Li和Be的丰度的信息比任何一种元素单独提供的都能揭示更多的内部过程信息。我们利用加拿大-法国-夏威夷望远镜以高光谱分辨率和高信噪比（S/N）对46颗类日恒星3131 Å处的Be II进行了观测。我们的Li i6707 Å中39颗恒星的数据来自我们使用夏威夷大学88英寸（2.2米）望远镜、谱仪和Keck I高分辨率梯队光谱仪进行的高分辨率、高信噪比观测，还有6颗恒星的数据来自文献。我们样本中的大多数恒星是F和G矮星，Teff在6100到6600 K之间，[Fe/H]在-0.6到+0.2之间。通过光谱合成确定了Be的丰度，而Li作为混合物进行分析以确定Li的丰度。我们在这些恒星中发现Li和Be的范围都很大；Be至少为2.5指数，Li至少为3指数。然而，正如Deliyannis等人从一个较小的样本中发现的那样，Li和Be之间存在极好的相关性。我们发现，在5850 K（靠近疏散星团中的Li“峰”）至6680 K（在Hyades定义的Li“隙”的底部）的Teff范围内，Li和Be似乎同时耗尽。这个显著的对数关系的斜率是0.36：当Li减少了10倍时，Be只减少了2.2倍。有一些不足的证据表明，较冷的恒星和较热的恒星之间的斜率发生了变化，使得较冷的恒星比较热的恒星消耗更多的Li相对Be。这些结果与包含旋转诱导的恒星表面物质与恒星深层物质缓慢混合的模型很好地吻合。
It is important to add observations of Be to the huge arsenal of Li observations in order to identify the mechanisms operating in stellar interiors that alter the surface composition of the light elements. Beryllium is more resistant to destruction than is Li, so information on the abundances of both Li and Be reveals more information on the internal processes than either element does alone. We have made observations of Be II at 3131 Å in 46 solar-type stars from the Canada-France-Hawaii Telescope with high spectral resolution and high signal-to-noise ratios (S/N). Our Li I 6707 Å data for 39 of these stars come from our high-resolution, high-S/N observations with the University of Hawai`i 88 inch (2.2 m) telescope and coudé spectrograph and Keck I High Resolution Echelle Spectrometer and, for six stars, from the literature. Most of the stars in our sample are F and G dwarfs with Teff between 6100 and 6600 K and with [Fe/H] between -0.6 and +0.2. The abundances of Be have been determined through spectrum synthesis, while Li has been analyzed as a blend to find the Li abundance. We find a large range in both Li and Be in these stars; for Be it is at least 2.5 dex and for Li at least 3 dex. However, there is an excellent correlation between Li and Be, as discovered by Deliyannis et al. from a smaller sample. We find that in the range of Teff of 5850 K (near the Li "peak" in open clusters) to 6680 K (at the bottom of the Li "gap" as defined by the Hyades), Li and Be appear to be depleted together. The slope of this remarkable logarithmic relation is 0.36: as Li is reduced by a factor of 10, Be is reduced by only 2.2 times. There is some scant evidence for a change in the slope between the cooler stars and the hotter stars such that the cooler stars deplete more Li relative to Be than the hotter stars. These results are well matched by models that incorporate rotationally induced slow mixing of the stellar surface material with the deeper layers of the star.