— ULTRA-METAL-POOR AND CARBON-RICH 1
— ULTRA-METAL-POOR AND CARBON-RICH 1
复制标题
— 极度贫金属和富含碳 1
DOI：
--
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
D. Reimers
中科院分区：
文献类型：
--
作者：
J. Norris;N. Christlieb;A. Korn;K. Eriksson;M. Bessell;T. Beers;L. Wisotzki;D. Reimers
我们报告了超贫金属红巨星HE 0557−4840的发现和高分辨率、高信噪比的光谱分析，它是目前已知的第三大重元素缺乏型星星。其大气参数为Teff = 4900 K，log g = 2.2，[Fe/H] =-4.75。这使得[Fe/H] < -4.0的恒星数量增加到了3颗，而HE 0557−4840的发现表明，银河系晕的金属丰度分布函数在[Fe/H] =-4.0和[Fe/H]=-5.3的两颗贫金属恒星之间没有“差距”。HE 0557−4840富含碳- [C/Fe] = +1.6 -这是三个天体共有的属性，[Fe/H] <-4.0，这表明众所周知的碳相对于铁的增加随着[Fe/H]的减少而达到其逻辑结论-无处不在的碳丰富-在最低丰度。我们还提出了另外18个元素的丰度（9个）和极限（9个）。对于那些有很好测量的丰度或很强的上限的物种，HE 0557−4840与[Fe/H] δ-4.0的大部分恒星相比是“正常的”-除了Co。虽然两者都没有提供明确的解决方案，但后者似乎更接近目标。需要进一步的数据来确定氧丰度并改善Co的丰度，从而更有力地限制该物体的起源。主题标题：银河号：编队-银河：光环-星星：丰度-恒星：个人HE 0557−4840 -早期宇宙-核反应，核合成，丰度
We report the discovery and high-resolution, high S/N , spectroscopic analysis of the ultra-metal-poor red giant HE 0557−4840, which is the third most heavy-element deficient star currently known. Its atmospheric parameters are Teff = 4900K, log g = 2.2, and [Fe/H] = –4.75. This brings the number of stars with [Fe/H] < –4.0 to three, and the discovery of HE 0557−4840 suggests that the metallicity distribution function of the Galactic halo does not have a “gap” between [Fe/H] = –4.0, where several stars are known, and the two most metal-poor stars, at [Fe/H] ∼ –5.3. HE 0557−4840 is carbon rich – [C/Fe] = +1.6 – a property shared by all three objects with [Fe/H] < −4.0, suggesting that the well-known increase of carbon relative to iron with decreasing [Fe/H] reaches its logical conclusion – ubiquitous carbon richness – at lowest abundance. We also present abundances (nine) and limits (nine) for a further 18 elements. For species having well-measured abundances or strong upper limits, HE 0557−4840 is “normal” in comparison with the bulk of the stellar population at [Fe/H] ∼ –4.0 – with the possible exception of Co. We discuss the implications of these results for chemical enrichment at the earliest times, in the context of single (“mixing and fallback”) and two-component enrichment models. While neither offers a clear solution, the latter appears closer to the mark. Further data are required to determine the oxygen abundance and improve that of Co, and hence more strongly constrain the origin of this object. Subject headings: Galaxy: formation — Galaxy: halo — stars: abundances — stars: individual HE 0557−4840 — early Universe — nuclear reactions, nucleosynthesis, abundances