Early chemical evolution of Zn driven by magnetorotational supernovae
  and the pathway to the solar Zn composition
  The site of Zn production remains an elusive and challenging problem in
astrophysics. A large enhancement of the [Zn/Fe] ratios of very metal-poor
stars in the Galactic halo suggests the death of short-lived massive stars,
i.e., core-collapse supernovae (CCSNe), as one major site for Zn production.
Previous studies have claimed that some specific CCSNe can produce Zn in
sufficient quantities. However, it remains unclear which models can withstand
the critical test of observations. Using a Zn abundance feature similar to that
of r-process elements in faint satellite galaxies, we find evidence that Zn
production took place through much rarer events than canonical CCSNe. This
finding can be unified with the implied decrease in the rate of Zn production
with an increasing metallicity for Galactic halo stars, which narrows down the
major site of Zn production in the early galaxy to magneto-rotational SNe
(MR-SNe). On the other hand, in the later phase of galactic evolution, we
predict that the major Zn-production site switched from MR-SNe to thermonuclear
SNe (SNe Ia). According to this scenario, an accumulation of the contributions
from two types of SNe eventually led to the solar isotope composition of Zn
which mainly owes 66,68Zn to MR-SNe and 64Zn to SNe Ia triggered by
He-detonation. The requirement of Zn production in SNe Ia sheds a new light on
the hot debate on the scenario for SN Ia progenitors, suggesting that a
He-detonation model might be one major channel for SNe Ia.
