RVels & metallicities of RR Lyrae stars from LAMOST

We present improved template-matching methods to determine the stellar atmospheric parameters of RRLs from single-epoch spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also known as the Guoshoujing Telescope (LAMOST). We determine the radial velocities and stellar atmospheric parameters (effective temperature Teff, surface gravity logg, and metallicity [M/H]) of 10486 and 1027 RRLs from 42729 LAMOST low-resolution spectra (LRS) and 7064 LAMOST medium-resolution spectra (MRS), respectively.

Our results are in good agreement with the parameters of other databases, where the external uncertainties of Teff, logg, and [M/H] for LRS/MRS are estimated to be 207/142K, 0.21/0.16dex, and 0.24/0.18dex, respectively. We conclude with the variation characteristics of the radial velocities (RV) and stellar atmospheric parameters for RRLs during the pulsation phase. There is a significant difference of 28+/-21km/s between the peak-to-peak amplitude (A_ptp_) of RV from the H{alpha} line (RV_H{alpha}_) and from metal lines (RV_metal_) for RRab, whereas it is only 4+/-17km/s for RRc.