Inferring the Progenitor Mass–Kinetic Energy Relation of Stripped-envelope Core-collapse Supernovae from Nebular Spectroscopy

The relation between the progenitor mass and the kinetic energy of the explosion is a key toward revealing the explosion mechanism of stripped-envelope core-collapse supernovae (SESNe). Here, we present a method to derive this relation using the nebular spectra of SESNe, based on the correlation between [O i ]/[Ca ii ], which is an indicator of progenitor mass, and the width of [O i ], which measures the expansion velocity of the oxygen-rich material. To explain the correlation, the kinetic energy ( E _K ) is required to be positively correlated with the progenitor mass as represented by the CO core mass ( M _CO ). We demonstrate that SNe IIb/Ib and SNe Ic/Ic-BL follow the same M _CO – E _K scaling relation, which suggests that helium-rich and helium-deficient SNe share the same explosion mechanism. The M _CO – E _K relation derived in this work is compared with the ones derived from early phase observations. The results are largely in good agreement. Combined with early phase observations, the method presented in this work provides a chance to scan through the ejecta from the outermost region to the dense inner core, which is important to reveal the global properties of the ejecta and constrain the explosion mechanism of core-collapse SNe.