Near-Ultraviolet Observations of HD 221170: New Insights into the Nature of r-Process-rich Stars
Near-Ultraviolet Observations of HD 221170: New Insights into the Nature of r-Process-rich Stars
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DOI：
10.1086/504069
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发表时间：
2006-04
期刊：
影响因子：
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通讯作者：
I. Ivans;J. Simmerer;C. Sneden;J. Lawler;J. Cowan;R. Gallino;S. Bisterzo
中科院分区：
文献类型：
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作者：
I. Ivans;J. Simmerer;C. Sneden;J. Lawler;J. Cowan;R. Gallino;S. Bisterzo
利用Keck I HIRES上的近紫外敏感探测器获得的高分辨率光谱，辅以麦克唐纳天文台2d- couddad获得的数据，我们对明亮的富含r过程的贫金属红巨星HD 221170进行了全面的化学成分分析。对57个独立的中性和电离物种的分析得出了46个元素的丰度，另外5个元素的丰度有显著的上限。利用~ 200fe峰跃迁导出了模型恒星大气参数。从35种中子捕获元素（Z bbb30）的350多个跃迁中，推导出了30种中子捕获元素的丰度和另外3种中子捕获元素的上限。利用La的36个跃迁，Eu的16个跃迁，Th的7个跃迁，我们得出了对数λ (Th/La) = -0.73 （σ = 0.06）和对数λ (Th/Eu) = -0.60 （σ = 0.05）的比值，这些值与之前从CS 22892-052、BD +17 3248和HD 115444等其他富r过程的贫金属恒星中得出的值非常吻合。根据Th/Eu天文钟，推断年龄为11.7±2.8 Gyr。较重的中子捕获元素（Z≥56）的丰度分布与预测的尺度太阳系r过程丰度很好地拟合，在其他r过程丰富的恒星中也可以看到。然而，与其他r过程丰富的恒星不同，我们发现HD 221170中较轻的中子俘获元素（37 < Z < 56）的丰度也与尺度太阳r过程模式预测的丰度一致。
Employing high-resolution spectra obtained with the near-UV-sensitive detector on the Keck I HIRES, supplemented by data obtained with the McDonald Observatory 2d-coudé, we have performed a comprehensive chemical composition analysis of the bright r-process-rich metal-poor red giant star HD 221170. Analysis of 57 individual neutral and ionized species yielded abundances for a total of 46 elements and significant upper limits for an additional five. Model stellar atmosphere parameters were derived with the aid of ~200 Fe peak transitions. From more than 350 transitions of 35 neutron-capture (Z > 30) species, abundances for 30 neutron-capture elements and upper limits for three others were derived. Utilizing 36 transitions of La, 16 of Eu, and seven of Th, we derive ratios of log ϵ(Th/La) = -0.73 (σ = 0.06) and log ϵ(Th/Eu) = -0.60 (σ = 0.05), values in excellent agreement with those previously derived for other r-process-rich metal-poor stars such as CS 22892-052, BD +17 3248, and HD 115444. Based on the Th/Eu chronometer, the inferred age is 11.7 ± 2.8 Gyr. The abundance distribution of the heavier neutron-capture elements (Z ≥ 56) is fitted well by the predicted scaled solar system r-process abundances, as also seen in other r-process-rich stars. Unlike other r-process-rich stars, however, we find that the abundances of the lighter neutron-capture elements (37 < Z < 56) in HD 221170 are also in agreement with the abundances predicted for the scaled solar r-process pattern.