A Triple-Energy-Source Model for Superluminous Supernova iPTF13ehe

Almost all superluminous supernovae (SLSNe) whose peak magnitudes are $\lesssim -21$ mag can be explained by the $^{56}$Ni-powered model, magnetar-powered (highly magnetized pulsar) model or ejecta-circumstellar medium (CSM) interaction model. Recently, iPTF13ehe challenges these energy-source models, because the spectral analysis shows that $\sim 2.5M_\odot$ of $^{56}$Ni have been synthesized but are inadequate to power the peak bolometric emission of iPTF13ehe, while the rebrightening of the late-time light-curve (LC) and the H$\alpha$ emission lines indicate that the ejecta-CSM interaction must play a key role in powering the late-time LC. Here we propose a triple-energy-source model, in which a magnetar together with some amount ($\lesssim 2.5M_\odot$) of $^{56}$Ni may power the early LC of iPTF13ehe while the late-time rebrightening can be quantitatively explained by an ejecta-CSM interaction. Furthermore, we suggest that iPTF13ehe is a genuine core-collapse supernova rather than a pulsational pair-instability supernova candidate. Further studies on similar SLSNe in the future would eventually shed light on their explosion and energy-source mechanisms.