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

arXiv:1004.2791v3 [astro-ph.HE] 28 Apr 2010 Mon. Not. R. Astron. Soc. 000, 1–53 (2009) Printed 28 May 2018 (MN LATEX style file v2.2) Numerical models of collisions between core-collapse supernovae and circumstellar shells Allard Jan van Marle1,2, Nathan Smith3, Stanley P. Owocki2 and B. van Veelen 4 1 Centre for Plasma Astrophysics, K.U. Leuven, Celestijnenlaan 200B, B-3001, Leuven, Belgium 2Bartol Research Institute, University of Delaware, Newark, DE 19716, USA 2Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720 4 Astronomical Institute, Utrecht University, P.O. Box 80 000, 3508 TA Utrecht, the Netherlands Submitted ??/?? ABSTRACT Recent observations of luminous Type IIn supernovae (SNe) provide com- pelling 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 col- lapse. 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 Mshell/MSN) 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⊙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 un- certain. The lightcurve shape and observed shell velocity can help diagnose the approximate size and density of the circumstellar shell, and it may be pos- sible to distinguish between spherical and bipolar shells with multiwavelength lightcurves. These models are merely illustrative. One can, of course, achieve 2 A. J. van Marle et al. even higher luminosities and longer duration light curves from interaction by increasing the explosion energy and shell mass beyond values adopted here. Key words: hydrodynamics — methods: numerical — stars: mass loss — stars: supernovae (general) — stars: winds, outflows 1 INTRODUCTION The luminosity of a supernova (SN) results from energy input by a combina- tion of radioactive decay and shock kinetic energy (see e.g., Arnett 1996), and for a Type II SN, the shape of the light curve depends on quantities like the star’s initial radius, ejecta mass, and explosion energy (Arnett 1996; Young 2004; Kasen & Woosley 2009). For SNe with small initial radii, like SNe of Types Ia, Ib, Ic, and peculiar SNe II like SN 1987A that result from blue su- pergiants, most of the shock-deposited thermal energy imparted to the stellar envelope is converted back into kinetic energy through adiabatic expansion, so nearly all of the observed luminosity comes from the radioactive decay of 56Ni and 56Co. In “normal” SNe II-P that result from the explosions of red supergiants (RSGs), however, the large initial radius allows some modest frac- tion (typically 1–2%) of the shock-deposited thermal energy to be radiated away, powering much of the plateau of the lightcurve, although the vast ma- jority still goes into expansion energy. At late times, even SNe II-P have their luminosity powered by radioactive decay (e.g., Hamuy 2003). Subsequently, however, as the fast SN ejecta expand, they can collide with dense circumstellar or interstellar material (CSM/ISM) that may surround the SN. As a result, additional kinetic energy may be transformed once again back into thermal energy through shock heating, which in turn may be lost by radiative cooling if a dense radiative shock forms (e.g., Chevalier & Fransson 2008). This can enhance the luminosity for long after the explosion: Som SNe remain radio luminous for decades (Montes et al. 1998; Williams et al. 2002; Van Dyk et al. 1993), and this interaction may power a visible super- nova remnant (SNR) such as Cas A for hundreds of years (Chevalier 1977; Chevalier & Oishi 2003). On the other hand, if the collision with dense CSM happens immediately after the explosion, it may significantly alter the spec- trum and light curve of the SN itself. This latter scenario is generally thought to be the case for the observed sub-class of Type IIn supernovae (Schlegel 1990; Filippenko 1997), where the “n” corresponds to “narrow” or intermediate- width H lines from the shock-heated CSM gas or decelerated SN ejecta (e.g. Chugai & Danziger 1994; Chugai 2001). Supernova collisions with circumstellar shells 3 In a normal SN, the expected re

…(Full text truncated)…

This content is AI-processed based on ArXiv data.