Two New r-process-enhanced Stars with [Fe/H] > −0.6 dex from the LAMOST-MRS Survey

Abstract

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 ∼ 7500) 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 3.5 m 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. TYC 1710-933-1 presents enhancement 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.