Origin of postmaximum bump in luminous type Ic SN 2019stc

Abstract

We address the issue of the postmaximum bump observed in the light curve of some superluminous supernovae. We rule out the popular mechanism of a circumstellar interaction suggested for the bump explanation. Instead we propose that the postmaximum bump is caused by the magnetar dipole field enhancement several months after the explosion. The modeling of SN 2019stc light curve based on the thin shell approximation implies that at the age of $\sim 90$ days the initial dipole magnetic field should be amplified by a factor of 2.8 to account for the postmaximum bump. The specific mechanism for the field amplification of the newborn magnetar on the timescale of several months has yet to be identified.