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

• Published in: 天文和天体物理学研究 Vol. 22; no. 7; pp. 109 - 117
• Main Authors: Xiao-Jin Xie, Jian-Rong Shi, Tian-Lu Chen, Hong-Liang Yan, Tian-Yi Chen, Kai-Ke Pan, Chun-Qian Li, Shuai Liu, Qi Gao, Tai-Sheng Yan, Ming-Yi Ding
• Format: Journal Article
• Language: English
• Published: Department of Physics,College of Science,Tibet University,Lhasa 850000,China 2022; School of Astronomy and Space Science,University of Chinese Academy of Sciences,Beijing 100049,China%Department of Physics,College of Science,Tibet University,Lhasa 850000,China; Astronomy Department,New Mexico State University,Las Cruces,New Mexico 88003,USA; Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100101,China; Key Laboratory of Cosmic Rays(Tibet University),Ministry of Education,Lhasa 850000,China%Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100101,China; Key Laboratory of Cosmic Rays(Tibet University),Ministry of Education,Lhasa 850000,China%Apache Point Observatory,Sunspot,New Mexico 88349,USA
• Subjects: stars:chemically peculiar; stars:fundamental parameters; stars:abundances
• ISSN: 1674-4527; 2397-6209

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.