Two new r-process-enhanced stars with [Fe/H] > −0.6 dex from the LAMOST-MRS survey

Abstract We report the discovery of two r-process-enhanced stars with [Fe/H] > −0.6 dex selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey. Three candidate stars have been selected from the LAMOST medium- resolution (R ∼ 7,500) spectroscopic survey, and the followed-up high signal-to-noise ratio and high-resolution (R ∼ 31,500) spectra are obtained with the ARC Echelle Spectrograph mounted on the 3.5m telescope at the Apache Point Observatory, which allow us for the determination of stellar atmospheric parameters and abundances of 20 elements. Among these three r-process-enhanced candidate stars, TYC 1710-933-1 and TYC 2858-372-1 have [Eu/Fe] higher than 0.3 dex and [Ba/Eu] lower than 0.0 dex, thus, can be identified as new r-process-enhanced objects. TYC 2858-372-1 shows similar r+s-process pattern to the Sun, while TYC 1710-933-1 presents enhancements of the r-process elements of Nd and Eu. Our work indicates that the enrichment mechanisms of the heavy neutron-capture elements are complicated for metal-rich stars.