  Both recent observations and stellar evolution models suggest that
pair-instability supernovae (PISNe) could occur in the local Universe, at
metallicities below Z_Sun/3. Previous PISN models were mostly produced at very
low metallicities in the context of the early Universe. We present new PISNe
models at a metallicity of Z=0.001, which are relevant for the local Universe.
We take the self-consistent stellar evolutionary models of pair-instability
progenitors with initial masses of 150 and 250 solar masses at metallicity of
Z=0.001 by Langer et al. (2007) and follow the evolution of these models
through the supernova explosions, using a hydrodynamics stellar evolution code
with an extensive nuclear network including 200 isotopes. Both models explode
as PISNe without leaving a compact stellar remnant. Our models produce a
nucleosynthetic pattern that is generally similar to that of Population III
PISN models, which is mainly characterized by the production of large amounts
of alpha-elements and a strong deficiency of the odd-charged elements. However,
the odd-even effect in our models is significantly weaker than that found in
Population III models. The comparison with the nucleosynthetic yields from
core-collapse supernovae at a similar metallicity (Z=0.002) indicates that
PISNe could have strongly influenced the chemical evolution below Z=0.002,
assuming a standard initial mass function. The odd-even effect is predicted to
be most prominent for the intermediate mass elements between silicon and
calcium. With future observations of chemical abundances in Population II
stars, our result can be used to constrain the number of PISNe that occurred
during the past evolution of our Galaxy.
