Numerical models of collisions between core-collapse supernovae and circumstellar shells

Abstract

Recent observations of luminous Type IIn supernovae (SNe) provide compelling evidence that massive circumstellar shells surround their progenitors. In this paper we investigate how the properties of such shells influence the SN light curve by conducting numerical simulations of the interaction between an expanding SN and a circumstellar shell ejected a few years prior to core collapse. Our parameter study explores how the emergent luminosity depends on a range of circumstellar shell masses, velocities, geometries and wind mass-loss rates, as well as variations in the SN mass and energy. We find that the shell mass is the most important parameter, in the sense that higher shell masses (or higher ratios of M shell /M SN ) lead to higher peak luminosities and higher efficiencies in converting shock energy into visual light. Lower mass shells can also cause high peak luminosities if the shell is slow or if the SN ejecta are very fast, but only for a short time. Sustaining a high luminosity for durations of more than 100 d requires massive circumstellar shells of the order of 10 M or more. This reaffirms previous comparisons between pre-SN shells and shells produced by giant eruptions of luminous blue variables (LBVs), although the physical mechanism responsible for these outbursts remains uncertain. The light-curve shape and observed shell velocity can help diagnose the approximate size and density of the circumstellar shell, and it may be possible to distinguish between spherical and bipolar shells with multi-wavelength light curves. These models are merely illustrative. One can, of course, achieve even higher luminosities and longer duration light curves from interaction by increasing the explosion energy and shell mass beyond values adopted here.

Finding the First Cosmic Explosions. Ii. Core-Collapse Supernovae

“…For example, if the shock collides with a dense shell ejected during a luminous blue variable (LBV) outburst prior to the SN, an extremely bright event in the UV can result that could be detected above z ∼15 (e.g., Smith & McCray 2007;van Marle et al 2010;Moriya et al 2010Moriya et al , 2013Tanaka et al 2012). We are now studying the observational signatures of these superluminous Pop III Type IIn SNe (Whalen et al 2013a).…”

Effect of Supernovae on the Local Interstellar Material

“…Other simulations have explored the evolution of the subsequent supernova shock waves within the bubbles [44,45,46,47,43,48]. Although the highly supersonic winds around massive stars (wind velocity on order 1000-2000 km s −1 ), and the low density and high pressure pervading the bubble would point to an extremely high temperature within the bulk of the bubble (of order 10 7 to 10 8 K), X-ray observations have shown that if hot gas is detected at all, its temperature and emission measure are both low, on the order of a few times 10 6 K [49,50,51,52].…”

Electron-capture supernovae exploding within their progenitor wind

“…The bolometric LC is obtained with the hydrodynamics code ZEUS-MP that is combined with a cooling function, which is applicable to the optically thin system. The method is similar to that adopted by van Marle et al (2010). The homologous SN ejecta is assumed to have two density components with n = 9 and δ = 0.…”