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

Allard Jan van Marle$^{1,2}$
Nathan Smith$^3$
Stan Owocki$^2$
Bob van Veelen$^4$

1-Centre for Plasma Astrophysics, K.U. Leuven, Celestijnenlaan 200B, B-3001, Leuven, Belgium
2-Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
3-Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720, USA
4-Astronomical Institute, Utrecht University, P.O. Box 80,000, 3508 TA Utrecht, the Netherlands

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 lightcurve 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 order 10~M_sol 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 lightcurve 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 multiwavelength
lightcurves. 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.

Reference: MNRAS in press, published online
Status: Manuscript has been accepted


Comments: Full tables of results available online with the paper.