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arXiv 2202.00767astro-ph.SRastro-ph.GA
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NGC 752 --一个两倍于毕宿星团年龄的疏散星团中的锂和铍

Lithium and Beryllium in NGC 752 -- An Open Cluster Twice the Age of the Hyades

Ann Merchant Boesgaard, Michael G. Lum, Ashley Chontos, Constantine P. Deliyannis

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12 pages, 11 color figures, 5 tables Accepted for publication in Ap.J
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摘要：

轻元素锂（Li）和铍（Be）的表面丰度揭示了恒星内部发生的物理过程的信息。对疏散星团恒星中这两种元素含量的研究表明，年龄对这些机制有影响。我们在凯克一号望远镜上用HIRES获得了高光谱分辨率和高信噪比的NGC 752主序星Li和Be的光谱。为了与其他星团进行有意义的比较，我们在一个共同的尺度上确定了恒星参数。我们已经发现了丰富的锂和Be的光谱合成技术。NGC 752的年龄是毕宿星团的两倍。我们发现：（1）在NGC 752中，以6500 K附近为中心的Li凹陷较宽，并向低温扩展，（2）在较老的NGC 752中，Be凹陷较深，（3）在6200 K附近的Li“峰”较低约0.3 dex，（4）在6200 K附近的Li“峰”较低约0.3 dex，（5）在6200 K附近的Li“峰”较低约0.3 dex。4）尽管较冷的恒星中Be的消耗很少，但NGC 752中的Be可能比毕宿星团中的Be低; 5）两个团簇的Li含量均随温度的降低而降低，但在一定温度下，NGC 752团簇中Li含量比NGC 752少$\sim$ 0.4 dex。这些差异与理论预测的轻元素核在表面对流区以下的输运是一致的。这两个星系团的旋转随温度变化的模式表明了它们与旋转自旋下降的联系。

英文摘要：

The surface abundances of the light elements lithium (Li) and beryllium (Be) reveal information about the physical processes taking place in stellar interiors. The investigation of the amount of these two elements in stars in open clusters shows the effect of age on those mechanisms. We have obtained spectra of both Li and Be in main-sequence stars in NGC 752 at high spectral resolution and high signal-to-noise ratios with HIRES on the Keck I telescope. In order to make meaningful comparisons with other clusters, we have determined the stellar parameters on a common scale. We have found abundances of Li and Be by spectral synthesis techniques. NGC 752 is twice the age of the well-studied Hyades cluster. We find that 1) The Li dip centered near 6500 K is wider in NGC 752, having expanded toward cooler temperatures; 2) The Be dip is deeper in the older NGC 752; 3) The Li "peak" near 6200 K is lower by about 0.3 dex; 4) Although there is little Be depletion in the cooler stars, it is possible that Be may be lower in NGC 752 than in the Hyades; 5) The Li content in both clusters declines with decreasing temperature, but there is less Li in NGC 752 at a given temperature by $\sim$0.4 dex. These differences are consistent with the transport of the light-element nuclei below the surface convection zone as predicted by theory. That connection to rotational spin-down is indicated by the pattern of rotation with temperature in the two clusters.

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