Boron in Lithium- and Beryllium-deficient F Stars
Boron in Lithium- and Beryllium-deficient F Stars
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缺乏锂和铍的 F 星中的硼
DOI：
10.1086/305059
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
D. Lambert
中科院分区：
文献类型：
--
作者：
A. Boesgaard;C. Deliyannis;A. Stephens;D. Lambert
戈达德高分辨率摄谱仪（GHRS）已与哈勃太空望远镜（HST）一起用于观测9颗金属丰度接近太阳的F和G矮星中2497 nm处的B I区。选星是因为他们有各种各样的理和被的不足。这9颗恒星中的大多数是最近在凯克I 10米望远镜、加拿大-法国-夏威夷3.6米望远镜和夏威夷大学2.2米望远镜上以高光谱分辨率和高信噪比观测到的，Be II的望远镜为3131 nm，Li I的望远镜为6708 nm。通过光谱合成，我们已经确定了我们的九颗程序星和来自HST档案的其他五颗恒星中B的丰度。我们所使用的恒星参数是以自洽的方式为程序星和档案星确定的。光谱合成也被用来确定锂和铍的丰度或上限。由于非LTE效应，对B和Li丰度进行了校正。恒星起源于Li（和Be）倾斜的ZAMS区域。尽管Li和Be存在很大的缺陷，但我们发现B丰度具有惊人的一致性，即，没有B蘸。在所有情况下，Li缺乏大于Be缺乏。在我们的样本中，温度最低、演化程度最高的星星--星云A，其B丰度比其他恒星的平均值低0.6 dex。这颗星星也有最大的Be缺乏（超过80倍）和最大的Li缺乏（超过600倍）。这些数据，连同其他研究的锂浸，强烈反对扩散和质量损失，并赞成缓慢混合的原因，锂和Be浸和没有一个B浸。6颗[Fe/H]从-0.75到+0.15的恒星的Be丰度范围从样品的最大值到最大值的4倍，但这些恒星的B/Be比值恒定在±0.10 dex以内，接近银河宇宙射线谱的预测值10-15。四颗太阳金属丰度的恒星的Be范围仍然是2倍，但B/Be比值恒定在±0.03 dex以内。这些结果意味着银河系宇宙射线产生的B和Be是不均匀的相对生产的元素，如铁恒星核合成。
The Goddard High Resolution Spectrograph (GHRS) has been used with the Hubble Space Telescope (HST) to observe the B I region at 2497 Å in nine F and G dwarfs of approximately solar metallicity. The stars were selected because they have a variety of Li and Be deficiencies. Most of the nine stars were newly observed at high spectral resolution and high signal-to-noise ratios at the Keck I 10 m telescope, the Canada-France-Hawaii 3.6 m telescope, and the University of Hawaii 2.2 m telescope at 3131 Å for Be II and 6708 Å for Li I. With spectrum synthesis we have determined the abundances of B in our nine program stars and in five other stars from the HST archive. The stellar parameters we have used have been determined in a self-consistent way for the program stars and the archive stars. Spectrum synthesis has also been used to determine the Li and Be abundances or upper limits. Corrections to the B and Li abundances due to non-LTE effects have been applied. The stars originate from the region on the ZAMS of the Li (and Be) dip. In spite of large deficiencies in Li and Be, we find a striking uniformity in the B abundances, i.e., there is no B dip. In all cases the Li deficiency is greater than the Be deficiency. For the coolest and most evolved star in our sample, ζ Her A, the B abundance is 0.6 dex lower than the mean for the other stars. This star also has the largest Be deficiency (more than a factor of 80) and the largest Li deficiency (more than a factor of 600). These data, together with other studies of the Li dip, argue strongly against diffusion and mass loss and in favor of slow mixing as the cause of the Li and Be dip and the absence of a B dip. Six stars with [Fe/H] from -0.75 to +0.15 have Be abundances ranging from the maximum of the sample to a factor of 4 below the maximum, yet these stars have a B/Be ratio that is constant to within ±0.10 dex and that is close to the predictions of Galactic cosmic-ray spallation of 10-15. The Be range for four stars with solar metallicity is still a factor of 2, and yet the B/Be ratio is constant to within ±0.03 dex. These results imply that the Galactic cosmic-ray production of B and Be is not uniform relative to the production of elements such as Fe by stellar nucleosynthesis.