不同光谱型的低分辨率恒星光谱在不同信噪比条件下视向速度测量精度的分析

恒星的视向速度对于研究银河系的演化结构和动力学有很重要的意义，同时也是寻找变源和特殊天体的一种手段。不同的研究对其测量精度有不一样的要求。使用模板匹配的方法计算不同类型的低分辨率可见光波段恒星光谱的视向速度精度，从而为不同方面的科学研究提供有效可靠的参考。分别选取不同光谱型高信噪比的美国斯隆巡天恒星光谱，并加以噪声来模拟不同信噪比条件下的恒星光谱。通过分别计算这些恒星样本的视向速度，定量分析了各种类型的恒星在不同信噪比条件下能达到的视向速度测量精度。同时，还就白矮星的视向速度测量精度进行了分析。结果显示，对于相同信噪比的早型恒星的视向速度测量精度远没有晚型恒星的测量精度高，尤其是A型星的视向速度测量标准误差是K型星和M型星的5~8倍。分析其原因，主要是由于不同类型恒星的具有不同宽度的谱线所导致的。因此对于具有更宽谱线的白矮星光谱的视向速度测量误差更大，可达50 km·s-1。以上结论将为恒星科学研究提供很好的参考。

The Radial Velocity Measurement Accuracy of Different Spectral Type Low Resolution Stellar Spectra at Different Signal-to-Noise Ratio

The radial velocity of the star is very important for the study of the dynamics structure and chemistry evolution of the Milky Way, is also an useful tool for looking for variable or special objects. In the present work, we focus on calculating the radial velocity of different spectral types of low-resolution stellar spectra by adopting a template matching method, so as to provide effective and reliable reference to the different aspects of scientific research. We choose high signal-to-noise ratio (SNR) spectra of different spectral type stellar from the Sloan Digital Sky Survey (SDSS), and add different noise to simulate the stellar spectra with different SNR. Then we obtain the radial velocity measurement accuracy of different spectral type stellar spectra at different SNR by employing a template matching method. Meanwhile, the radial velocity measurement accuracy of white dwarf stars is analyzed as well. We concluded that the accuracy of radial velocity measurements of early-type stars is much higher than late-type ones. For example, the 1-sigma standard error of radial velocity measurements of A-type stars is 5~8 times as large as K-type and M-type stars. We discuss the reason and suggest that the very narrow lines of late-type stars ensure the accuracy of measurement of radial velocities, while the early-type stars with very wide Balmer lines, such as A-type stars, become sensitive to noise and obtain low accuracy of radial velocities. For the spectra of white dwarfs stars, the standard error of radial velocity measurement could be over 50 km·s-1 because of their extremely wide Balmer lines. The above conclusion will provide a good reference for stellar scientific study.