Phase Ii Of The Lamost-Kepler/K2 Survey. I. Time Series Of Medium-Resolution Spectroscopic Observations

Phase II of the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST)-Kepler/K2 survey (LK-MRS), initiated in 2018, aims at collecting medium-resolution spectra (R similar to 7500; hereafter MRS) for more than 50,000 stars with multiple visits (similar to 60 epochs) over a period of 5 yr (2018 September to 2023 June). We selected 20 footprints distributed across the Kepler field and six K2 campaigns, with each plate containing a number of stars ranging from similar to 2000 to similar to 3000. During the first year of observations, the LK-MRS has already visited 13 plates 223 times over 40 individual nights, and collected similar to 280,000 and similar to 369,000 high-quality spectra in the blue and red wavelength ranges, respectively. The atmospheric parameters and radial velocities for similar to 259,000 spectra of 21,053 targets were successfully calculated by the LAMOST stellar parameter pipeline. The internal uncertainties for the effective temperature, surface gravity, metallicity, and radial velocity are found to be 100 K, 0.15 dex, 0.09 dex, and 1.00 km s(-1), respectively, when derived from a medium-resolution LAMOST spectrum with a signal-to-noise ratio (S/N) in the g band of 10. All of the uncertainties decrease as S/N increases, but they stabilize for S/N > 100. We found 14,997, 20,091, and 1514 stars in common with the targets from the LAMOST low-resolution survey (LRS), Gaia, and the Apache Point Observatory Galactic Evolution Experiment (APOGEE), respectively, corresponding to fractions of similar to 70%, similar to 95%, and similar to 7.2%. In general, the parameters derived from LK-MRS spectra are consistent with those obtained from the LRS and APOGEE spectra, but the scatter increases as the surface gravity decreases when comparing with the measurements from APOGEE. A large discrepancy is found with the Gaia values of the effective temperature. Comparisons of the radial velocities of LK-MRS to Gaia and LK-MRS to APOGEE nearly follow a Gaussian distribution with means of mu similar to 1.10 and 0.73 km s(-1), respectively. We expect that the results from the LK-MRS spectra will shed new light on binary stars, asteroseismology, stellar activity, and other research fields.