Four-hundred Very Metal-poor Stars studied with LAMOST and Subaru. I. Survey Design, Follow-up Program, and Binary Frequency

TL;DR

This study presents a large survey of approximately 400 very metal-poor stars, analyzing their elemental abundances, binary frequency, and kinematics to understand early Galactic chemical evolution.

Contribution

It introduces a comprehensive survey combining LAMOST and Subaru data, reports on binary star detection at low metallicity, and provides radial velocities and kinematic analysis.

Findings

Identification of seven double-lined spectroscopic binaries.

Radial velocities for the entire sample are reported.

Discussion on the binary frequency at very low metallicity.

Abstract

The chemical abundances of very metal-poor stars provide important constraints on the nucleosynthesis of the first generation of stars and early chemical evolution of the Galaxy. We have obtained high-resolution spectra with the Subaru Telescope for candidates of very metal-poor stars selected with a large survey of Galactic stars carried out with LAMOST. In this series of papers, we report on the elemental abundances of about 400 very metal-poor stars and discuss the kinematics of the sample obtained by combining the radial velocities measured in this study and recent astrometry obtained with Gaia. This paper provides an overview of our survey and follow-up program, and reports radial velocities for the whole sample. We identify seven double-lined spectroscopic binaries from our high-resolution spectra, for which radial velocities of the components are reported. We discuss the frequency of such relatively short-period binaries at very low metallicity.