Rubidium in Metal-deficient Disk and Halo Stars
Rubidium in Metal-deficient Disk and Halo Stars
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缺金属盘和晕星中的铷
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
D. Lambert
中科院分区：
文献类型：
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作者：
J. Tomkin;D. Lambert
我们报告了第一次对恒星Rb丰度的广泛研究。在44颗金属丰度范围为-2.0 < [Fe/H] < 0.0的矮星和巨星中，利用高分辨率光谱测定或设定了重元素及其伴生元素Y、Zr和Ba的丰度上限。在缺乏金属的恒星中，Rb相对于Fe是系统地过多的；我们发现32颗[Fe/H] < -0.5且测量Rb的恒星的平均[Rb/Fe]为+0.21。这种行为与Y， Zr和Ba形成鲜明对比，除了三颗新的CH恒星（HD 23439A和B和BD +5°3640）外，它们在同一颗恒星中相对于铁一直略有不足；除3颗CH星外，我们发现[Fe/H] < -0.5的恒星的平均[Y/Fe]、[Zr/Fe]和[Ba/Fe]分别为-0.19（24颗星）、-0.12（28颗星）和-0.06（29颗星）。Rb与Y、Zr和Ba的不同行为部分可以归因于在太阳和这些恒星中Rb具有较大的r过程成分，而Y、Zr和Ba主要是s过程元素，只有较小的r过程成分。此外，Rb s过程丰度与s处理点的中子密度有关。已发表的对富s过程红巨星Rb的观测表明，贫金属巨星的中子密度更高。这些观测表明，在金属贫乏的恒星中，Rb的s过程丰度更高。计算出的Rb r-过程丰度（恒星Eu丰度的估计）和s-过程丰度（红巨星的估计）的组合，令人满意地解释了[Rb/Fe]与[Fe/H]的运行。
We report the first extensive study of stellar Rb abundances. High-resolution spectra have been used to determine, or set upper limits on, the abundances of this heavy element and the associated elements Y, Zr, and Ba in 44 dwarfs and giants with metallicities spanning the range -2.0 < [Fe/H] < 0.0. In metal-deficient stars Rb is systematically overabundant relative to Fe; we find an average [Rb/Fe] of +0.21 for the 32 stars with [Fe/H] < -0.5 and measured Rb. This behavior contrasts with that of Y, Zr, and Ba, which, with the exception of three new CH stars (HD 23439A and B and BD +5°3640), are consistently slightly deficient relative to Fe in the same stars; excluding the three CH stars, we find that the stars with [Fe/H] < -0.5 have average [Y/Fe], [Zr/Fe], and [Ba/Fe] of -0.19 (24 stars), -0.12 (28 stars), and -0.06 (29 stars), respectively. The different behavior of Rb on the one hand and Y, Zr, and Ba on the other can be attributed in part to the fact that in the Sun and in these stars Rb has a large r-process component while Y, Zr, and Ba are mostly s-process elements with only small r-process components. In addition, the Rb s-process abundance is dependent on the neutron density at the s-processing site. Published observations of Rb in s-process enriched red giants indicate a higher neutron density in the metal-poor giants. These observations imply a higher s-process abundance for Rb in metal-poor stars. The calculated combination of the Rb r-process abundance, as estimated for the stellar Eu abundances, and the s-process abundance, as estimated for red giants, accounts satisfactorily for the observed run of [Rb/Fe] with [Fe/H].