DA白矮星视向速度测量

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英文篇名：Radial Velocity Measurement of the DA White Dwarfs 作者：赵颖玥 ; 罗阿理 英文作者：Zhao Yingyue;Luo Ali;Beijing Zhongguancun High School;Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences; 关键词：白矮星 ; 视向速度 ; 模板匹配 英文关键词：White dwarf;;Radial velocity;;Template match 中文刊名：YTWT 英文刊名：Astronomical Research & Technology 机构：北京市中关村中学;中国科学院光学天文重点实验室(国家天文台); 出版日期：2018-09-04 10:37 出版单位：天文研究与技术 年：2019 期：v.16;No.61 基金：国家自然科学基金(11703051);; 973项目(2014CB845704)资助 语种：中文; 页：YTWT201901001 页数：7 CN：01 ISSN：53-1189/P 分类号：5-11

摘要

DA白矮星光谱在光学波段主要由巴尔默线主导,谱线比较宽,且谱线轮廓不对称,传统的线心方法确定视向速度非常困难。介绍了一种基于利用白矮星的有效温度(Teff)和表面重力加速度(log g)选择理论模板,通过交叉相关方法确定DA白矮星的APP速度,减去白矮星的引力红移得到白矮星的视向速度。测试发现对于有效温度高于10 000 K且信噪比大于20的DA白矮星的低分辨率光谱(R～2000),精度在10 km/s以内。基于这种方法测量了SDSS DR7的DA白矮星观测样本的视向速度,统计发现在1 000 pc内,视向速度的平均值接近于0。
        White Dwarfs(WDs) are the final stage of the evolution of the majority of low-and medium-mass stars with initial mass <8 M⊙.Approximately 75% of all observed WDs are DA type.The spectra of DA white dwarf are dominated with Balmer Hydrogen lines.It is very difficult to measure the APP radial velocity of WDs by the line center because of the wide and asymmetry spectral profile.The kinematics of WDs is very important to distinguish populations of WDs.This paper presents a method for APP radial velocity measurement using cross-correlation between the observed spectrum and the template spectrum that has similar parameters,which has advantage than line center method,and the template spectra are from theoretical spectra by Koster et al.The final radial velocity is derived by the difference of APP radial velocity and the gravitational redshift.After test with simulated spectrum,the accuracy is within 10 km/s for DA white dwarfs with Te ff higher than 10000 K and SNR larger than 20.In addition,the radial velocities of observed DA WDs from SDSS DR7 are measured with the above method.The average radial velocities of these close DA white dwarfs(distance <1000 pc) are approaching zero.

引文

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