We report chemical abundances of 14 young α-rich stars including neutron-capture elements based on high-quality optical spectra from HIRES/Keck I and differential line-by-line analysis. From the comparison of the abundance patterns of young α-rich stars to those of nearby bright red giants with a similar metallicity range (−0.7<[Fe/H]<−0.2), we confirm their high α-element abundances reported by previous studies based on near-infrared spectroscopy. We reveal for the first time low abundances of s-process elements and high abundances of r-process elements. All the abundances are consistent with those seen in typical α-rich population of the Galactic disk, and no abundance anomalies are found except for Li-enhancement in one object previously reported and mild enhancement of Na in two stars. In particular, the lack of s-process enhancement excludes the hypothesis that mass transfer from asymptotic giant branch stars plays an important role in the formation of young α-rich stars. The high frequency of radial velocity variation (more than 50%) is also confirmed. We argue that mass transfer from low-mass red giants is the likely dominant formation mechanism for young α-rich stars.
@article{arxiv.1804.08818,
title = {Optical high-resolution spectroscopy of 14 young $\alpha$-rich stars},
author = {Tadafumi Matsuno and David Yong and Wako Aoki and Miho N. Ishigaki},
journal= {arXiv preprint arXiv:1804.08818},
year = {2018}
}