统计SDSS-DR7中的CEMP星并分析其温度和光谱型  

Statistics of Effective Temperatures and Spectral Types of Carbon-Enhanced Metal-Poor(CEMP)Stars in the SDSS-DR7

作　　者：王凤飞[1,2] 罗阿理[1] 张健楠[1] 刘超[1] 赵永恒[1] 

机构地区：[1]中国科学院国家天文台,北京100012 [2]中国科学院研究生院,北京100049

出　　处：《天文研究与技术》2009年第3期167-174,共8页Astronomical Research & Technology

基　　金：国家自然科学基金(60402041)

摘　　要：统计了SDSS（TheSloanDigitalSkySurvey）最新发布的DR7（DataRelease7）数据中的CEMP星（Carbon—EnhancedMetal—PoorStars）。分析了样本的温度、光谱型、颜色等物理参量，同时给出了CEMP星在SDSS贫金属星中占的比例约为11％。统计得到SDSS_SSPP（TheSEGUEStellarParameterPipeline）发布的CEMP星样本的温度主要集中在6000～9000K范围内。采用PLSR（偏最小二乘回归）方法计算样本的温度并给出其光谱型，结果显示与SSPP发布的温度比较没有系统误差，但在温度较高时，随机误差较大，这与SSPP中采用不同方法给出的温度值是一致的。从颜色一颜色图上看，选出的CEMP星主要包含两类星：BHB／BS和F（FTurn-Off），前者温度较高且温度误差相对较大。通过样本在Log（g）一颜色图上的划分，可以区分BHB和BS样本。最后讨论了BHB／BS和F（FTurn-Off）中C元素的来源。The fraction of CEMP（ Carbon-Enhanced Metal-Poor）stars among metal-poor stars according to the SDSS （The Sloan Digital Sky Survey） DR7 （ Data Release 7 ） is about 11%. The effective temperatures of CEMP stars calculated with the SSPP（ The SEGUE Stellar Parameter Pipeline）are mostly in the range 6000K to 9000K. After recalculating the temperatures and the spectral types of CEMP stars by using the PLSR （Partial Least Squares Regression）method, we find that the results given by SSPP have larger random errors. In addition, the random deviotions bias in effective temperature between PLSR and SSPP cannot be ignored when the temperature is above 7500K. These are consistent with the estimates from different methods in the SSPP. Based on color-color and color-magnitude diagrams, CEMP stars can be divided into two categories： BHB/BS and F（F Turn-Off） , with the former category including stars of higher temperatures and larger errors in temperature values. The BHB and BS CEMP stars can also be separated in a log （g）-color diagram. Finally, possible origins of the carbon element in the two categories of CEMP stars are discussed.

关 键 词：SDSS DR7 CEMP 有效温度 光谱型 PLSR 

分 类 号：P144.1[天文地球—天体物理]