On the Energy Sources of the Most Luminous Supernova ASASSN-15lh

Abstract

In this paper, we investigate the energy-source models for the most luminous supernova ASASSN-15lh. We revisit the ejecta–circumstellar medium (CSM) interaction (CSI) model and the CSI plus magnetar spin-down with full gamma-ray/X-ray trapping, which were adopted by Chatzopoulos et al., and find that the two models cannot fit the bolometric light curve (LC) of ASASSN-15lh. Therefore, we consider a CSI plus magnetar model with the gamma-ray/X-ray leakage effect to eliminate the late-time excess of the theoretical LC. We find that this revised model can reproduce the bolometric LC of ASASSN-15lh. Moreover, we construct a new hybrid model (i.e., the CSI plus fallback model), and find that it can also reproduce the bolometric LC of ASASSN-15lh. Assuming that the conversion efficiency ( η ) of fallback accretion to an outflow is typically ∼10 −3 , we derive that the total mass accreted is ∼3.9 M ⊙ . The inferred CSM mass in the two models is rather large, indicating that the progenitor could have experienced an eruption of hydrogen-poor materials followed by an energetic core-collapse explosion leaving behind a magnetar or a black hole.