Self-Consistent Stellar Radial Velocities From Lamost Medium-Resolution Survey Dr7
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES(2021)
摘要
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. LAMOST Medium-resolution Survey (MRS) DR7 contains five million single-exposure stellar spectra with spectral resolution R similar to 7500. However, the temporal variation of the RV zero-points (RVZPs) of the MRS, which makes the RVs from multiple epochs inconsistent, has not been addressed. In this paper, we measure the RVs of 3.8 million single-exposure spectra (for 0.6 million stars) with signal-to-noise ratios (S/N) higher than 5 based on the cross-correlation function method, and propose a robust method to self-consistently determine the RVZPs exposure by exposure for each spectrograph with the help of Gaia DR2 RVs. Such RVZPs are estimated for 3.6 million RVs and can reach a mean precision of similar to 0.38 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 analyses. Validating the results with APOGEE DR16 shows that our absolute RVs can reach an overall precision of 0.84/0.80 km s(-1) in the blue/red arm at 50 < S/N < 100 and of 1.26/1.99 km s(-1) at 5 < S/N < 10. The cumulative distribution function of the standard deviations of multiple RVs (Nobs. 8) for 678 standard stars reaches 0.45/0.54, 1.07/1.39, and 1.45/1.86 km s(-1) in the blue/red arm at the 50%, 90%, and 95% levels, respectively. Catalogs of the RVs, RVZPs, and selected candidate RV standard stars are available at https://github.com/hypergravity/paperdata.
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关键词
dr7,self-consistent,medium-resolution
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