We calculate a nonlinear growth of the Rayleigh-Taylor instability in the exploding red supergiant stars with a two-dimensional hydrodynamical code, and examine how the extent of mixing depends on the progenitor's core mass and the envelope mass. The results are compared with the observations of type II-P supernovae and the recent type II-b supernova 1993J.

Introduction

Large scale mixing in supernova ejecta has been indicated in spectroscopic and photometric observations of various types of supernovae. This has stimulated 2D and 3D hydrodynamical calculations of the Rayleigh-Taylor (R-T) instabilities during supernova explosions for SN 1987A (Arnett et al. 1989; Hachisu et al. 1990, 1992; Fryxell et al. 1991; Müller et al. 1991; Den et al. 1990; Yamada et al. 1990; Yamada & Sato 1991; Herant & Benz 1991, 1992), type Ib/Ic supernovae (Hachisu et al. 1991, 1994a), type II-P supernovae (Herant & Woosley 1994; Hachisu et al. 1994b), and the type II-b supernova 1993J (Iwamoto et al. 1994). In particular, Hachisu et al. (1991, 1994a) found that development of the R-T instabilities depend sensitively on the presupernova structure, so that the comparison between hydrodynamical simulations and observations can provide a new clue to the understanding of supernova progenitors, their structure, and the explosion mechanism.

In the present paper, we follow a nonlinear growth of the R-T instabilities in the exploding red supergiant stars, i.e., type II-P and II-b supernovae. We find that the extent of mixing depends on the core mass and the envelope mass of red supergiants.