Importance of 56 Ni production on diagnosing explosion mechanism of core-collapse supernova.

56Ni is an important indicator of the supernova explosions, which characterizes light curves. Nevertheless, rather than 56Ni, explosion energy has often been paid attention from explosion mechanism community, since it is, at a glance, easier to estimate from numerical data than the amount of 56Ni. The final explosion energy, however, is difficult to estimate by detailed numerical simulations because current simulations cannot reach typical time-scale of saturation of the explosion energy. Instead, the amount of 56Ni converges within a short time-scale so that it would be a more robust probe of the explosion mechanism. We investigated the amount of 56Ni synthesized by explosive nucleosynthesis in supernova ejecta by means of numerical simulations and an analytic model. For numerical simulations, we employ a Lagrangian hydrodynamics code in which neutrino heating and cooling terms are taken into account by the light-bulb approximation. We additionally develop an analytic model, which gives a reasonable estimate of the amount of 56Ni. We find that, in order to produce enough amount of 56Ni, |$\mathcal {O}(1)$| Bethe s−1 of growth rate of the explosion energy is needed, which is much larger than those found in recent exploding simulations, typically |$\mathcal {O}(0.1)$| Bethe s−1. We also find that a progenitor model with a large compactness parameter leads to efficient synthesis of 56Ni, opposite to the explodability that prefers a small compactness. These two results may indicate that there is a limited parameter space in the properties of the progenitor stars, which can explain both the explodability and 56Ni production simultaneously. [ABSTRACT FROM AUTHOR]