We present results of simulations of stellar collapse and explosions in spherical symmetry for progenitor stars in the 8– 10 M _ { \odot } range with an O-Ne-Mg core .
The simulations were continued until nearly one second after core bounce and were performed with the Prometheus/Vertex code with a variable Eddington factor solver for the neutrino transport , including a state-of-the-art treatment of neutrino-matter interactions .
Particular effort was made to implement nuclear burning and electron capture rates with sufficient accuracy to ensure a smooth continuation , without transients , from the progenitor evolution to core collapse .
Using two different nuclear equations of state ( EoSs ) , a soft version of the Lattimer & Swesty EoS and the significantly stiffer Wolff & Hillebrandt EoS , we found no prompt explosions , but instead delayed explosions , powered by neutrino heating and the neutrino-driven baryonic wind which sets in about 200 ms after bounce .
The models eject little nickel ( < 0.015 M _ { \odot } ) , explode with an energy of \ga 0.1 \times 10 ^ { 51 } erg , and leave behind neutron stars ( NSs ) with a baryonic mass near 1.36 M _ { \odot } .
Different from previous models of such explosions , the ejecta during the first second have a proton-to-baryon ratio of Y _ { e } \ga 0.46 , which suggests a chemical composition that is not in conflict with galactic abundances .
No low-entropy matter with Y _ { e } \ll 0.5 is ejected .
This excludes such explosions as sites of a low-entropy r-process .
The low explosion energy and nucleosynthetic implications are compatible with the observed properties of the Crab supernova , and the small nickel mass supports the possibility that our models explain some subluminous Type II-P supernovae .