Superluminous light curves from supernovae exploding in a dense wind

Observations from the last decade have indicated the existence of a general class of superluminous supernovae (SLSNe), in which the peak luminosity exceeds 10⁴⁴ erg s^-1. Here we focus on a subclass of these events, where the light curve is also tens of days wide, so the total radiated energy is of order 10⁵¹ erg. If the origin of these SLSNe is a core-collapse-driven explosion of a massive star, then the mechanism that converts the explosion energy into radiation must be very efficient (much more than in typical core-collapse SNe, where this efficiency is of order 1%). We examine the scenario where the radiated luminosity is due to efficient conversion of kinetic energy of the ejected stellar envelope into radiation by interaction with an optically thick, pre-existing circumstellar material, presumably the product of a steady wind from the progenitor. We base the analysis on analytical derivations of various limits, and on a simple, numerically solved, hydrodynamic diffusion model, which allows us to explore the regime of interest, which does not correspond to the analytical limits. In our results, we identify the qualitative behavior of the observable light curves, and relate them to the parameters of the wind. We specifically show that a wide and superluminous supernova requires the mass of the relevant wind material to be comparable to that of the ejected material from the exploding progenitor. We find the wind parameters that explain the peak luminosity and width of the bolometric light curves of three particular SLSNe, namely, SN 2005ap, SN 2006gy, and SN 2010gx, and show that they are best fitted with a wind that extends to a radius of order 10¹⁵ cm. These results serve as an additional indication that at least some SLSNe may be powered by interaction of the ejected material with a steady wind of similar mass.