LC analysis of type I superluminous SNe

We also find a moderate correlation ({rho}~0.5; p~0.01) between the phase of the bumps and the rise time, implying that such bumps tend to happen at a certain "evolutionary phase," (3.7+/-1.4)t_rise_. Most bumps are consistent with having diffused from a central source of variable luminosity, although sources further out in the ejecta are not excluded. With this evidence, we explore whether the cause of these bumps is intrinsic to the supernova (e.g., a variable central engine) or extrinsic (e.g., circumstellar interaction).

Both cases are plausible, requiring low- level variability in the magnetar input luminosity, small decreases in the ejecta opacity, or a thin circumstellar shell or disk.