利用LAMOST光谱和Kepler星震学数据搜寻α超丰的年轻恒星

Context: The young α-rich stars are the stars whose ages are younger than 6 Gyr but the α abundance are larger than 0.13 dex. The recent discovery of α-rich young stars has challenged the standard theory of stellar evolution. The born place, chemical enrichment process and the distribution of these stars are not well understood. The study of these stars provides new insight into the stellar mixing and evolution. However, they are only handful of stars known so far. Thus, it is necessary to embark a systematic survey to search for such stars and we found LAMOST database with millions of giant stars spectra would be an appropriate database to initiate our study..Contents: (1) Develop new methods of estimating the stellar α abundance; (2) Develop new methods of estimating the ages and mass of red giants; (3) Search for and identify the α-rich young stars..Merits: (1) This is the first project to search for the α-rich young stars with the LAMOST spectra and Kepler asteroseismic data, which could increase the number of α rich young stars by one order; (2) The new algorithms of estimating the ages of red giants will be used; (3) The new methods of estimating the α abundance of stars from LAMOST spectra will be provided..Foundation: Have tested our Extreme Learning Method to a subsample of LAMOST spectra to derive alpha abundances and they are in good agreement with the literature values.

项目背景: α超丰的年轻恒星是丰度大于0.13 dex 但年龄小于6Gyr的恒星。这类恒星的发现挑战了传统的恒星演化理论，对其深入研究有助于我们深入理解恒星形成和演化过程，为银河系的演化理论提供观测限制。目前该类恒星样本极少，限制了对其深入研究，有必要利用LAMOST数据系统开展这类恒星的搜寻证认工作。.研究内容：(1) LAMOST恒星的α丰度估计方法研究；(2) 基于星震学数据的红巨星年龄的估计方法研究；(3) α超丰的年轻恒星的搜寻与证认。.项目特色：(1) 首次使用LAMOST光谱结合Kepler星震学数据系统搜寻α超丰的年轻恒星，将使样本数量提高一个量级；(2) 使用全新的算法估计红巨星的年龄和质量；(3) 全面系统的研究LAMOST光谱的α丰度估计方法。.项目基础：已完成LAMOST恒星的α丰度估计。

项目主要研究内容包括（1）低分辨率光谱的恒星α丰度的估计。针对SDSS光谱和LAMOST光谱提出了基于ELM算法与LASSO算法的恒星\alpha丰度估计方法，为确定LAMOST光谱的α丰度提供了算法基础；（2）红巨星质量与年龄估计的新算法研究。针对红巨星质量与年龄估计的难题，提出了使用已有的红巨星质量和年龄数据，基于机器学习算法估计质量和年龄的新方法。实验证实该方法具有较高精度；（3）筛选出了α超丰年轻恒星的候选体；（4）研究过程中在LAMOST数据集中还发现了一类特殊恒星—热亚矮星，并给出了56颗全新的热亚矮星样本。.通过三年的研究，在恒星的参数估计、红巨星的质量与年龄估计、α超丰恒星的筛选、特殊恒星的挖掘方面取得了超出了基金任务书目标的研究成果。共发表与课题相关的学术论文6篇，部分成果被多次引用。这些成果为后续深入的科学研究提供了基础。.项目期间课题组成员共参加国内外学术会议7次，组织学术会议1次，与国内外学者专家进行充分的探讨和技术交流，为今后的学术研究和技术合作搭建了理想的平台；人才培养方面取得了很大的进展，课题组三位讲师晋升为副教授，并成为硕士生导师，一名教师晋升为高级实验师。所取得的成果和工作基础为今后的课题研究奠定了基础。