碳超丰贫金属拐点星的搜寻与丰度分析  

Searching for Carbon-enhanced Metal-poor Main-sequence Turnoff Stars and the Abundances Analysis

作　　者：张世琳 李海宁 赵刚[1,2] Zhang Shilin;Li Haining;Zhao Gang(Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100101,China;School of Astronomy and Space Science,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院光学天文重点实验室(国家天文台),北京100101 [2]中国科学院大学天文与空间科学学院,北京100049

出　　处：《天文研究与技术》2020年第1期27-38,共12页Astronomical Research & Technology

基　　金：国家自然科学基金(11890694,11573032)资助.

摘　　要：碳超丰贫金属星在老年恒星中的普遍存在使得它成为研究宇宙早期形成和演化的重要对象,具有不同中子俘获元素丰度特征的碳超丰贫金属星有不同的起源。不同于已经历挖掘过程的巨星,主序拐点星能很好地在其表层大气保留形成初期的物质,从而可以追溯到更早期的恒星形成化学环境。通过LAMOST巡天数据选源并利用Subaru/HDS进行后续高分辨率光谱观测了12颗碳超丰贫金属星主序拐点星,其中有10颗星是首次被分析。与已有的碳超丰贫金属星主序拐点星观测样本相比,文中的样本包含了更高比例的中子俘获元素不超丰碳超丰贫金属恒星(CEMP-no星),发生在中等程度碳超丰区域,为其起源研究提供了重要数据。对其中6颗CEMP-no星测定了锂丰度,尤其是其中3颗极贫金属星样本,为探讨[Fe/H]<-3.0的碳超丰贫金属星拐点星锂丰度特征提供了重要的新观测数据。新增样本验证了CEMP-no星在[Fe/H]^-3.0附近为锂-正常星,与前人结论一致;而新增的两颗CEMP-s星表现出了中等锂丰度,介于之前的较大锂丰度范围,研究为CEMP-s和CEMP-no的分类提供了辅助约束条件。Decades of studies on metal-poor stars reveal that there are large fraction of metal-poor stars showing enhancement in carbon.Carbon-enhanced metal-poor(CEMP)stars are believed to be the trace of the first nucleosynthesis process and the chemical composition of the interstellar medium at the early stage of the universe.Different abundance patterns of neutron-capture elements reflect different origins of CEMP stars.Main-sequence turnoff stars are believed to preserve primordial material in its surface atmosphere since its birth date and place,as they have not suffered from dilution,whereas giants should have already gone through at least the first dredge-up.We report high-resolution abundances analysis of 12 CEMP turnoff stars which are selected from LAMOST survey and follow-up observed with Subaru/HDS.Among them,ten are analyzed for the first time.Compared with previous works,our sample includes larger fractions of CEMP-no(indicating carbon enrichment,but no enhancement in neutron-capture elements)stars,proving important new data for moderately C-enriched metal-poor turnoff stars.Especially,this sample provides Li abundance measurements for six CEMP-no stars including three extremely metal-poor ones whose current sample is still limited.The new sample confirmed that,when it comes to regions around[Fe/H]^-3.0,CEMP-no stars show normal lithium abundances while CEMP-s stars are usually depleted in lithium.

关 键 词：元素丰度 碳超丰贫金属星 拐点星 锂丰度 

分 类 号：P141.5[天文地球—天体物理]