红亚矮星研究进展

红亚矮星是甚小质量恒星中的贫金属成员,质量从约0.5M⊙ (M⊙为太阳质量)到H燃烧的最小质量(0.075M⊙～0.085M⊙,取决于金属丰度),其寿命长于哈勃年龄,是银河系结构和化学增丰史的重要示踪体.与银盘上数量最多的恒星成员红矮星不同,红亚矮星在太阳附近非常稀少,并且其运动学特征与盘矮星有较大差异,属于年老银河系...

Research Development of Red Subdwarfs

Red subdwarfs are metal-poor very low mass stars(VLMs)with the mass of 0.5M⊙to 0.08M⊙and lifetime longer than the Hubble time.They are supposed to be able to provide crucial information for star formation and metal enrichment history of the Milky Way.Differing from the red dwarfs which are the most dominant members of the Milky Way,red subdwarfs are rare in the solar neighborhood,and they have kinematic properties associated with halo and thick disk.These low mass stars are named as subdwarfs because they are located under the dwarfs of the main sequence on the H-R diagram.In addition,the large proper-motions and characteristic spectral features of red subdwarfs can help distinguish them from red dwarfs.In the optical band,the spectrum of a subdwarf is dominated by the oxide(such as TiO and VO)and hydride(such as CaH).According to the spectral morphology and molecular bands,red subdwarfs can be divided into several spectral types and metallicity subclasses.The masses of the coolest subdwarfs are close to the hydrogen burning limit.A subdwarf with the lowest mass may be a star or a young brown dwarf.Historical background and frontier knowledge of the studies of red subdwarfs are introduced.The recent development of red subdwarf researches is summarized,including samples,kinematic properties,atmospheric parameter estimates,mass and temperature ranges,activity analysis,and the multiplicity.Besides,the importance of the spectral analysis method in the study of subdwarfs is discussed in detail.Finally,the method of classification of subdwarfs based on spectral features and the way to use the latest stellar atmospheric model to estimate the atmospheric parameters of red subdwarfs are introduced.