M矮星是银河系中最普遍的恒星, 它们的运动状况能提供银河系演化的线索, 视向速度(RV)是反映M矮星运动状况的重要参数之一。 我国的大科学工程LAMOST巡天项目已经获得了数十万M型星光谱, 测量这些恒星的视向速度需要自动、 高效的程序。 计算M矮星视向速度的一般方法是将观测光谱与模板光谱进行交叉相关得出。 然而在实际处理过程中, 由于本质上的不同或者噪声的影响, 一些观测光谱和模板光谱错误匹配, 从而使得这些光谱的视向速度测量产生偏差。 为了减少噪声等因素的影响, 对于信噪比较高、 但局部有较强噪声的光谱, 采用统计与经验特征相结合的方法选取光谱中的有效特征段、 避开噪声污染的波段计算M型星的视向速度。 利用该方法对LAMOST DR3 M型星星表中的部分实测光谱测量了视向速度, 将之与APOGEE星表中的对应视向速度进行了对比。 结果表明该方法有效地减少了局部噪声对视向速度的影响, 提高了视向速度测量的准确率。

M dwarfs are the most common stars in the Milky Way, and their motion brings to light the evolution of the Milky Way. Radial velocity (RV) of M dwarf is one of the most important parameters to reflect its motion. Chinese large scale scientific construction project LAMOST survey has obtained hundreds of thousands of M-type stars and their radial velocities measurement which needs the automatic and efficient program. The most commonly used method of measuring the radial velocity of an M star is to cross correlation between its observed spectra and the template spectra. However, in the actual process, idiosyncrasies of individual spectra and noises often lead to the loss of accuracy of radial velocities. To alleviate the effect induced by the above factors, in this paper, we try to improve radial velocities measurement of M dwarfs especially for those spectra with higher signal noise ratio but with local noises. A statistical method combining experienced features is proposed to select discriminative wavelength ranges of spectra for radial velocity measurement, avoiding noise affected wavelength regions. Some spectra from LAMOST DR3 M-type catalogue are used to test this method and the results are compared with the radial velocities of the same target from APOGEE. The experimental results show that the proposed method can effectively improve the accuracy of radial velocity measurement for M-type stars by reducing the influence of local spectral noises.