Nucleosynthesis Constraints on the Energy Growth Timescale of a Core-collapse Supernova Explosion

TL;DR

This study uses nucleosynthesis calculations to constrain the explosion timescale of core-collapse supernovae, finding that rapid explosions within 250 milliseconds best match observational data, challenging slower explosion models.

Contribution

It provides nucleosynthetic diagnostics that strongly favor rapid supernova explosion mechanisms over slower ones, based on observational constraints.

Findings

Rapid explosions ($t_{grow} \\lesssim 250$ ms) align with observed nucleosynthesis.

Nearly instantaneous explosions ($t_{grow} \\lesssim 50$ ms) best match observations.

Slow explosion models ($t_{grow} \\gtrsim 1000$ ms) are inconsistent with observational constraints.

Abstract

Details of the explosion mechanism of core-collapse supernovae (CCSNe) are not yet fully understood. There is an increasing number of numerical examples by ab-initio core-collapse simulations leading to an explosion. Most, if not all, of the ab-initio core-collapse simulations represent a `slow' explosion in which the observed explosion energy ($\sim 10^{51}$ ergs) is reached in a timescale of $\gtrsim1$ second. It is, however, unclear whether such a slow explosion is consistent with observations. In this work, by performing nuclear reaction network calculations for a range of the explosion timescale $t_{\rm grow}$, from the rapid to slow models, we aim at providing nucleosynthetic diagnostics on the explosion timescale. We employ one-dimensional hydrodynamic and nucleosynthesis simulations above the proto-neutron star core, by parameterizing the nature of the explosion mechanism by $t_{\rm grow}$. The results are then compared to various observational constraints; the masses of $^{56}$Ni derived for typical CCSNe, the masses of $^{57}$Ni and $^{44}$Ti observed for SN 1987A, and the abundance patterns observed in extremely metal-poor stars. We find that these observational constraints are consistent with the `rapid' explosion ($t_{\rm grow} \lesssim 250$ ms), and especially the best match is found for a nearly instantaneous explosion ($t_{\rm grow} \lesssim 50$ ms). Our finding places a strong constraint on the explosion mechanism; the slow mechanism ($t_{\rm grow} \gtrsim 1000$ ms) would not satisfy these constraints, and the ab-inito simulations will need to realize a rapid explosion.