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