Electron-capture supernovae as the origin of elements beyond iron
  We examine electron-capture supernovae (ECSNe) as sources of elements heavier
than iron in the solar system and in Galactic halo stars. Nucleosynthesis
calculations are performed on the basis of thermodynamic histories of mass
elements from a fully self-consistent, two-dimensional (2D) hydrodynamic
explosion model of an ECSN. We find that neutron-rich convective lumps with an
electron fraction down to Ye,min=0.40, which are absent in the one-dimensional
(1D) counterpart, allow for interesting production of elements between the iron
group and N=50 nuclei (from Zn to Zr, with little Ga) in nuclear
(quasi-)equilibrium. Our models yield very good agreement with the Ge, Sr, Y,
and Zr abundances of r-process deficient Galactic halo stars and constrain the
occurrence of ECSNe to ~4% of all stellar core-collapse events. If tiny amounts
of additional material with slightly lower Ye,min down to ~0.30-0.35 were also
ejected - which presently cannot be excluded because of the limitations of
resolution and two-dimensionality of the model -, a weak r-process can yield
elements beyond N=50 up to Pd, Ag, and Cd as observed in the r-process
deficient stars.
