Extremely Energetic Supernova Explosions Embedded in a Massive Circumstellar Medium: The Case of SN 2016aps

We perform one-dimensional radiation-hydrodynamic simulations of energetic supernova (SN) ejecta colliding with a massive circumstellar medium (CSM) aimed at explaining SN 2016aps, likely the brightest SN observed to date. SN 2016aps was a superluminous Type IIn SN, which released as much as $\gtrsim 5\times {10}^{51}$ erg of thermal radiation. Our results suggest that the multiband light curve of SN 2016aps is well explained by the collision of a $30M_{\odot }$ SN ejecta with the explosion energy of 10⁵² erg and a $\simeq 8M_{\odot }$ wind-like CSM with the outer radius of 10¹⁶ cm, that is, a hypernova explosion embedded in a massive CSM. This finding indicates that very massive stars with initial masses larger than $40M_{\odot }$, which supposedly produce highly energetic SNe, occasionally eject their hydrogen-rich envelopes shortly before the core collapse. We suggest that the pulsational pair-instability SNe may provide a natural explanation for the massive CSM and the energetic explosion. We also provide the relations among the peak luminosity, the radiated energy and the rise time for interacting SNe with the kinetic energy of 10⁵² erg, which can be used for interpreting SN 2016aps–like objects in future surveys.