Radial velocity measurements from LAMOST medium-resolution spectroscopic observations: A pointing towards the Kepler field

Radial velocityis one of key measurements in understanding the fundamental properties of stars, stellar clusters and the Galaxy. A plate of stars in the Keplerfield were observed in May of 2018 with the medium-resolution spectrographsof LAMOST, aiming to test the performance of this new system which is the upgraded equipment of LAMOSTafter the first five-year regular survey.We present our analysis on the radial velocitymeasurements (RVs) derived from these data. The results show that slight and significant systematic errorsexist among the RVs obtained from the spectra collected by different spectrographsand exposures, respectively. After correcting the systematic errorswith different techniques, the precision of RVs reaches ~1.3, ~1.0, ~0.5 and ~0.3 km/s at S/Nr = 10, 20, 50, and 100, respectively. Comparing with the RVs of the standard stars of the APOGEE survey, our RVs are calibrated with a zero-point shift of ~7 km/s. The results indicate that the LAMOSTmedium-resolution spectroscopic system may provide RVs in a reasonable accuracyand precisionfor the selected targets.