Boron Depletion in F and G Dwarf Stars and the Beryllium-Boron Correlation
Boron Depletion in F and G Dwarf Stars and the Beryllium-Boron Correlation
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F 和 G 矮星中的硼耗尽以及铍-硼相关性
DOI：
10.1086/427687
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
A. Steinhauer
中科院分区：
文献类型：
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作者：
A. Boesgaard;C. Deliyannis;A. Steinhauer
硼在恒星表面下提供了一个特殊的探测器，因为它比Li和Be能存活到更深的地方。为了寻找B的耗竭，我们在13颗Be耗尽较大的F和G矮星中观测到了B；为了比较，我们还获得了Li和Be未耗尽的五颗恒星的光谱。我们用高能扫描和STI获得了2497ä的B-I共振线的光谱。光谱分辨率为30,000或114,000，中值信噪比为70像素-1。在Keck I获得了新的Be和Li光谱，其中四颗标准星的分辨率为48,000。用MOOG光谱合成法测定了其丰度。标准恒星和严重的Be贫乏恒星之间的比较表明，0.22Dex的两组恒星的B丰度有明显的差异。我们发现了Be丰度和B丰度之间的相关性。A(Be)和A(B)NLTE之间的斜率为0.22±0.05[其中A(Element)=logN(Element)/N(H)+12.00]，如预期的那样，该斜率比A(Li)和A(Be)之间的斜率0.38要浅。我们利用最近发表的Be与[Fe/H]和B与[Fe/H]之间的经验关系，对轻元素丰度进行了归一化处理，以解释低金属丰度恒星的初始丰度较低的观测结果。归一化A(BE)和A(B)NLTE之间的相关性斜率为0.18±0.06。主序Ba星HR-107的Be丰度也最大，其B丰度比标准星低3.5倍。
Boron provides a special probe below the stellar surface since it survives to greater depths than do Li and Be. To search for B depletions we have observed B in 13 F and G dwarfs with large Be depletions; for comparison we have also obtained spectra of five stars that are undepleted in Li and Be. We have used HST with STIS to obtain spectra of the B I resonance line at 2497 Å. The spectral resolution is 30,000 or 114,000, and the median signal-to-noise ratio is 70 pixel-1. New Be and Li spectra have been obtained at Keck I with HIRES of four of the five standard stars at ~48,000 resolution. Abundances have been determined by the spectrum synthesis method with MOOG. A comparison between the standard stars and those with severe Be depletions shows a distinct difference in the B abundances between the two groups of 0.22 dex. We have discovered a correlation between the Be and B abundances. The slope between A(Be) and A(B)NLTE is 0.22 ± 0.05 [where A(element) = log N(element)/N(H) + 12.00], which, as expected, is shallower than the slope between A(Li) and A(Be) of 0.38. We have normalized the light-element abundances to account for the observation that the initial abundances are somewhat lower in lower metallicity stars by employing recently published empirical relations between Be and [Fe/H] and between B and [Fe/H]. The correlation between the normalized A(Be) and A(B)NLTE has a slope of 0.18 ± 0.06. The star with the largest Be depletion, HR 107, a main-sequence Ba star, also has the largest B depletion, with the B abundance lower by a factor of 3.5 relative to the standard stars.