We perform hydrodynamical calculations of the collision between the supernova ejecta and circumstellar matter for SN 1987A and SN 1993J. For SN 1987A we predict light curves of X-ray emissions from the shocked ring. For SN 1993J, thermal X-rays from the shocked circumstellar matter can consistently account for the observations with ROSAT, ASCA, and OSSE.

Introduction

The supernova ejecta collides with the circumstellar matter (CSM) if its progenitor was undergoing significant mass loss. Shock waves arising from this collision compress and heat the ejecta and the CSM. The emission from the shocked material strongly depends on the density distributions of the ejecta and the CSM, thereby providing important information about the nature of the CSM.

SN 1987A

The images from the European Southern Observatory (ESO) (Wampler et al. 1990) and the Hubble Space Telescope (HST) (Jakobsen et al. 1991) revealed the presence of a ring-like structure at ∼ 6 × 1017 cm from SN 1987A. The outermost part of the supernova ejecta is expanding at ∼ 104 km s−1 (Shigeyama & Nomoto 1990), thus being expected to collide with the ring at ∼ 10 years after the explosion.

Hydrodynamical model

The progenitor of SN 1987A had once become a red supergiant (RSG) and then contracted to a blue supergiant (BSG) before the explosion (for reviews, see Arnett et al. 1989, Hillebrandt & Höflich 1989, Podsiadlowski 1992, and Nomoto et al. 1993a).