# Importance of $^{56}$Ni production on diagnosing explosion mechanism of core-collapse supernova

## TL;DR

This paper emphasizes the importance of $^{56}$Ni production as a diagnostic tool for supernova explosion mechanisms, proposing that its measurement offers a more reliable indicator than explosion energy, which is harder to estimate.

## Contribution

The study introduces an analytic model and numerical simulations to better estimate $^{56}$Ni synthesis, highlighting its significance over explosion energy in understanding supernova mechanisms.

## Key findings

- $^{56}$Ni amount converges quickly, making it a reliable probe.
- A high growth rate of explosion energy is required to produce sufficient $^{56}$Ni.
- Current simulations underestimate the growth rate needed for observed $^{56}$Ni levels.

## Abstract

$^{56}$Ni is an important indicator of the supernova explosions, which characterizes light curves. Nevertheless, rather than $^{56}$Ni, the explosion energy has often been paid attention from the explosion mechanism community, since it is easier to estimate from numerical data than the amount of $^{56}$Ni. The final explosion energy, however, is difficult to estimate by detailed numerical simulations because current simulations cannot reach typical timescale of saturation of explosion energy. Instead, the amount of $^{56}$Ni converges within a short timescale so that it would be a better probe of the explosion mechanism. We investigated the amount of $^{56}$Ni synthesized by explosive nucleosynthesis in supernova ejecta by means of numerical simulations and an analytic model. For numerical simulations, we employ Lagrangian hydrodynamics code in which neutrino heating and cooling terms are taken into account by light-bulb approximation. Initial conditions are taken from Woosley & Hegel (2007), which have 12, 15, 20, and 25 $M_\odot$ in zero age main sequence. We additionally develop an analytic model, which gives a reasonable estimate of the amount of $^{56}$Ni. We found that, in order to produce enough amount of $^{56}$Ni, $\mathcal{O}(1)$ Bethe s$^{-1}$ of growth rate of the explosion energy is needed, which is much larger than that found in recent exploding simulations, typically $\mathcal{O}(0.1)$ Bethe s$^{-1}$.