A high-resolution spectral analysis of three carbon-enhanced metal-poor stars*
A high-resolution spectral analysis of three carbon-enhanced metal-poor stars*
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DOI：
10.1111/j.1365-2966.2006.10877.x
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发表时间：
2006-08
影响因子：
4.8
通讯作者：
A. Goswami;W. Aoki;T. Beers;N. Christlieb;J. Norris;S. Ryan;S. Tsangarides
中科院分区：
文献类型：
--
作者：
A. Goswami;W. Aoki;T. Beers;N. Christlieb;J. Norris;S. Ryan;S. Tsangarides
我们展示了使用斯巴鲁望远镜高色散摄谱仪获得的高分辨率光谱 (R � 50000) 的分析结果，其中包括从汉堡/ESO 棱镜巡天中选出的两颗碳增强贫金属 (CEMP) 恒星 HE 1305+0007 和 HE 1152 0355，以及经典 CH 星 HD 5223。所有这些恒星的有效温度都相对较低(4000–4750K) 和高碳丰度，导致其光谱中存在非常强的分子碳带。这些恒星的恒星大气参数表明它们的表面重力均与红巨星分支上的当前位置一致，金属丰度为 [Fe/H] = 2.0 (HE 1305+0007, HD 5223) 和 [Fe/H] = 1.3 (HE 1152 0355)。除了碳的大幅增强（[C/Fe]分别 = +1.8、+1.6 和 +0.6）之外，所有三颗恒星都表现出相对于铁的过程元素的强烈增强。 HE 1305+0007 表现出第三峰 s 过程元素铅的大幅增强，[Pb/Fe] = +2.37，以及高丰度的 r 过程元素铕，[Eu/Fe] = +1.97。发现第二峰 s 过程元素 Ba、La、Ce、Nd 和 Sm 比第一峰 s 过程元素 Zr、Sr 和 Y 的增强程度更高。因此，HE 1305+0007 加入了不断增长的所谓“先导星”类别，以及同时存在 r 过程和 s 过程元素的天体类别，即 CEMP-r/s 星。 HE 1152 0355 和 HD 5223 表现出的 n 捕获元素的大幅增强与 CH 星中普遍观察到的丰度模式更加一致，本质上是由纯 s 过程核合成产生的。根据现有的 CH 恒星形成理论以及 CEMP-r/s 群建议的形成情景，讨论了在这些恒星中观察到的元素丰度分布。
We present results of an analysis of high-resolution spectra (R � 50000), obtained with the Subaru Telescope High Dispersion Spectrograph, of two CarbonEnhanced Metal-Poor (CEMP) stars selected from the Hamburg/ESO prism survey, HE 1305+0007 and HE 1152 0355, and of the classical CH star HD 5223. All of these stars have relatively low effective temperatures (4000–4750K) and high carbon abundances, which results in the presence of very strong molecular carbon bands in their spectra. The stellar atmospheric parameters for these stars indicate that they all have surface gravities consistent with a present location on the red-giant branch, and metallicities of [Fe/H] = 2.0 (HE 1305+0007, HD 5223) and [Fe/H] = 1.3 (HE 1152 0355). In addition to their large enhancements of carbon ([C/Fe] = +1.8, +1.6 and +0.6. respectively), all three stars exhibit strong enhancements of the sprocess elements relative to iron. HE 1305+0007 exhibits a large enhancement of the 3rd-peak s-process element lead, with [Pb/Fe] = +2.37, as well as a high abundance of the r-process element europium, [Eu/Fe] = +1.97. The 2nd-peak s-process elements Ba, La, Ce, Nd, and Sm are found to be more enhanced than the 1st-peak s-process elements Zr, Sr and Y. Thus, HE 1305+0007 joins the growing class of the so-called “Lead Stars”, and also the class of objects that exhibit the presence of both r-process and s-process elements, the CEMP-r/s stars. The large enhancement of n-capture elements exhibited by HE 1152 0355 and HD 5223 are more consistent with the abundance patterns generally noticed in CH stars, essentially arising from pure s-process nucleosynthesis. The elemental abundance distributions observed in these stars are discussed in the light of existing theories of CH star formation, as well as the suggested formation scenarios of the CEMP-r/s group.