Abstract

The conventional wisdom that a Type II supernova explosion occurs inside a spherical stellar wind bubble blown by the wind of the red supergiant progenitor misses two important points: the progenitor wind may be time-dependent, and it may be asymmetric. These two features of SN progenitor winds have been well illustrated by the ring observed around SN 1987A. The existence of this circumstellar shell directly implies a time-dependence in the wind on time scales less than about 10,000 years. Also, the shell is undeniably asymmetric, implying some form of asymmetry in the progenitor wind(s). Some of the theories for an asymmetric circumstellar medium include gravitational focussing in a wide binary, rotationally deformed wind, colliding winds in a binary system, and asymmetric mass ejection in a common envelope or accretion phase of a close binary system. The wind dynamics of these various theories will be reviewed with an eye toward understanding the true history of Sk -69°202.