First Star Survivors as Metal-Rich Halo Stars that Experienced Supernova Explosions in Binary Systems

TL;DR

This paper proposes a new scenario where first stars in binary systems survive supernova explosions and are observed today as metal-rich halo stars, linking early universe star formation to current observations.

Contribution

It introduces a novel formation pathway for surviving first stars in binary systems, explaining their presence as metal-rich halo stars in our Galaxy.

Findings

Identification of candidate metal-rich halo stars with first star origins.

Models show supernova ejecta can enrich low-mass companions to observed metallicities.

Supports a new star formation channel in the early universe.

Abstract

The search for the first stars formed from metal-free gas in the universe is one of the key issues in astronomy because it relates to many fields, such as the formation of stars and galaxies, the evolution of the universe, and the origin of elements. It is not still clear if metal-free first stars can be found in the present universe. These first stars are thought to exist among extremely metal-poor stars in the halo of our Galaxy. Here we propose a new scenario for the formation of low-mass first stars that have survived until today and observational counterparts in our Galaxy. The first stars in binary systems, consisting of massive- and low-mass stars, are examined using stellar evolution models, simulations of supernova ejecta colliding with low-mass companions, and comparisons with observed data. These first star survivors will be observed as metal-rich halo stars in our Galaxy. We may have identified a candidate star in the observational database where elemental abundances and kinematic data are available. Our models also account for the existence of several solar-metallicity stars in the literature having space velocities equivalent to the halo population. The proposed scenario demands a new channel of star formation in the early universe and is a supplementary scenario for the origin of the known metal-poor stars.