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arXiv · 2105.11624

Self-consistent Stellar Radial Velocities from LAMOST Medium-Resolution Survey (MRS) DR7

Bo Zhang·Jiao Li·Fan Yang·Jian-Ping Xiong·Jian-Ning Fu·Chao Liu·Hao Tian·Yin-Bi Li·Jia-Xin Wang·Cai-Xia Liang·Yu-Tao Zhou·Wei-kai Zong·Cheng-Qun Yang·Nian Liu·Yong-Hui Hou
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Abstract

Radial velocity (RV) is among the most fundamental physical quantities obtainable from stellar spectra and is rather important in the analysis of time-domain phenomena. The LAMOST Medium-Resolution Survey (MRS) DR7 contains 5 million single-exposure stellar spectra at spectral resolution $R\sim7\,500$. However, the temporal variation of the RV zero-points (RVZPs) of the MRS survey, which makes the RVs from multiple epochs inconsistent, has not been addressed. In this paper, we measure the RVs of the 3.8 million single-exposure spectra (for 0.6 million stars) with signal-to-noise ratio (SNR) higher than 5 based on cross-correlation function (CCF) method, and propose a robust method to self-consistently determine the RVZPs exposure-by-exposure for each spectrograph with the help of \textit{Gaia} DR2 RVs. Such RVZPs are estimated for 3.6 million RVs and can reach a mean precision of $\sim 0.38\,\mathrm{km\,s}^{-1}$. The result of the temporal variation of RVZPs indicates that our algorithm is efficient and necessary before we use the absolute RVs to perform time-domain analysis. Validating the results with APOGEE DR16 shows that our absolute RVs can reach an overall precision of 0.84/0.80 $\mathrm{km\,s}^{-1}$ in the blue/red arm at $50<\mathrm{SNR}<100$, while 1.26/1.99 $\mathrm{km\,s}^{-1}$ at $5<\mathrm{SNR}<10$. The cumulative distribution function (CDF) of the standard deviations of multiple RVs ($N_\mathrm{obs}\geq 8$) for 678 standard stars reach 0.45/0.54, 1.07/1.39, and 1.45/1.86 $\mathrm{km\,s}^{-1}$ in the blue/red arm at 50\%, 90\%, and 95\% levels, respectively. The catalogs of the RVs, RVZPs, and selected candidate RV standard stars are available at \url{https://github.com/hypergravity/paperdata}.

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Bo Zhang, Jiao Li, Fan Yang, Jian-Ping Xiong, Jian-Ning Fu, Chao Liu, Hao Tian, Yin-Bi Li, Jia-Xin Wang, Cai-Xia Liang, Yu-Tao Zhou, Wei-kai Zong, Cheng-Qun Yang, Nian Liu, Yong-Hui Hou. 2021-05-25. Self-consistent Stellar Radial Velocities from LAMOST Medium-Resolution Survey (MRS) DR7. https://doi.org/10.3847/1538-4365%2Fac0834

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