  We provide progenitor models for electron capture supernovae (ECSNe) with
detailed evolutionary calculation. We include minor electron capture nuclei
using a large nuclear reaction network with updated reaction rates. For
electron captures, the Coulomb correction on the rates is treated and
contribution of neutron-rich nuclei is taken into account in the nuclear
statistical equilibrium (NSE) composition. We calculate the evolution of the
most massive super asymptotic giant branch stars and show that these stars
undergo off-center carbon burnings and form ONe cores at the center. These
cores get heavier up to the critical mass of 1.367 Msun and keep contracting
even after the initiation of O+Ne deflagration. Though inclusion of minor
electron capture nuclei causes convective URCA process at the contraction
phase, such process will have minor effect on the evolution. On the other hand,
electron captures by neutron-rich nuclei in the NSE region have more
significant effect. Also, we discuss the uniqueness of the critical core mass
for ECSNe and the effect of mass loss on the plausibility of our models for
ECSN progenitors.
