2019ApJ...886...47S

Details of the explosion mechanism of core-collapse supernovae (CCSNe) are not yet fully understood. There are 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 (∼10⁵¹ erg) is reached in a timescale of >=1 s. 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_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_grow. The results are then compared to various observational constraints: the masses of ⁵⁶Ni derived for typical CCSNe, the masses of ⁵⁷Ni and ⁴⁴Ti 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_grow <= 250 ms), and especially the best match is found for a nearly instantaneous explosion (t_grow <= 50 ms). Our finding places a strong constraint on the explosion mechanism; the slow mechanism (t_grow >= 1000 ms) would not satisfy these constraints, and the ab initio simulations will need to realize a rapid explosion.