DYNAMICS OF KEPLER SUPERNOVA REMNANT

Observations of Kepler's supernova remnant (SNR) have revealed a strong interaction with the ambient medium, far in excess of that expected at a distance of approximately 600 pc away from the Galactic plane where Kepler's SNR is located. This has been interpreted as a result of the interaction of supernova ejecta with the dense circumstellar medium (CSM). Based on the bow-shock model of Bandiera, we study the dynamics of this interaction. The CSM distribution consists of an undisturbed stellar wind of a moving supernova progenitor and a dense shell formed in its interaction with a tenuous interstellar medium. Supernova ejecta drive a blast wave through the stellar wind which splits into the transmitted and reflected shocks upon hitting this bow-shock shell. We identify the transmitted shock with the nonradiative, Balmer-dominated shocks found recently in Kepler's SNR. The transmitted shock most probably penetrated the shell in the vicinity of the stagnation point. A characteristic double-shell structure forms afterwards, consisting of the dense shocked shell and dense ejecta, with the hot, tenuous shocked wind gas between them. Two-dimensional hydrodynamical simulations reveal this structure to be Rayleigh-Taylor unstable. These results are in good agreement with the observed morphology of the remnant.