A Magnetar Engine and Circumstellar Medium Interaction: Synergistic Effects in Producing Superluminous Supernovae

Abstract

Superluminous supernovae (SLSNe) are often modeled as being powered either by a central engine or by strong interaction with dense circumstellar material (CSM). These two mechanisms may be dynamically coupled if the ejecta interact with dense CSM while being energized by a newborn magnetar. We develop a semi-analytical hybrid model that follows the coupled dynamics, energy conversion, and radiative output of such systems. A rapidly rotating magnetar injects energy through a relativistic wind, inflating a hot bubble inside the expanding ejecta. Part of the injected energy is stored as radiation, while the rest is converted into bulk kinetic energy of the swept-up ejecta. At the same time, the outer ejecta collide with the surrounding CSM and form a circumstellar interaction (CSI) region. As the shock driven by the magnetar accelerates through the ejecta, it can catch up with the CSI region and take over the subsequent interaction with the unshocked CSM. The emergent light curves are therefore governed by the coupled effects of magnetar energy injection, shock heating, and radiative diffusion. We show that this hybrid model can produce diverse SLSN light-curve morphologies, including luminous interaction-powered peaks, asymmetric post-peak declines, and late-time emission sustained by delayed leakage of magnetar-powered radiation. The model provides a plausible way to reduce the extreme nickel-mass or initial explosion-energy requirements often encountered in purely radioactive or purely interaction-powered interpretations.