Properties of Radial Velocities measurement based on LAMOST-II Medium-Resolution Spectroscopic Observations

R. Wang, A. -L. Luo, J. -J. Chen, Z. -R. Bai, L. Chen, X. -F. Chen, S. -B. Dong, B. Du, J. -N. Fu, Z. -W. Han, J. -L. Hou, Y. -H. Hou, W. Hou, D. -K. Jiang, X. Kong, L. -F. Li, C. Liu, J. -M. Liu, L. Qin, J. -R. Shi, H. Tian, H. Wu, C. -J. Wu, J. -W. Xie, H. -T. Zhang, S. Zhang, G. Zhao, Y. -H. Zhao, J. Zhong, W. -K. Zong, F. Zuo

Published 2019-08-13Version 1

The radial velocity (RV) is a basic physical quantity which can be determined through Doppler shift of the spectrum of a star. The precision of RV measurement depends on the resolution of the spectrum we used and the accuracy of wavelength calibration. In this work, radial velocities of LAMOST-II medium resolution (R ~ 7500) spectra are measured for 1,594,956 spectra (each spectrum has two wavebands) through matching with templates. A set of RV standard stars are used to recalibrate the zero point of the measurement, and some reference sets with RVs derived from medium/high-resolution observations are used to evaluate the accuracy of the measurement. Comparing with reference sets, the accuracy of our measurement can get 0.0227 km s/1 with respect to radial velocities standard stars. The intrinsic precision is estimated with the multiple observations of single stars, which can achieve to 1.36 km s/1,1.08 km s/1, 0.91 km s/1 for the spectra at signal-to-noise levels of 10, 20, 50, respectively.