Supernova Circumstellar Interaction

Publications

• Abstract: We study the evolution of supernova remnants in the circumstellar medium formed by mass loss from the progenitor star. The properties of this interaction are investigated, and the specific case of a 35 $\msun$ star is studied in detail. The evolution of the SN shock wave in this case may have a bearing on other SNRs evolving in wind-blown bubbles, especially SN 1987A.

• Abstract: During their lifetime, massive stars lose considerable mass in the form of stellar winds. These winds may evacuate a cavity in the surrounding medium, bordered by a dense shell. If the star ends its life in a supernova explosion, the resulting shock wave will interact with this shell. The subsequent evolution of the supernova remnant depends in particular on the ratio of the mass of the shell to the ejecta mass. Using numerical techniques this evolution is studied for a range of parameter values.

• Abstract: We summarize various aspects of the interaction of supernova remnants (SNRs) with the ambient medium. We discuss the evolution of SNRs in environments sculpted by the progenitor star, and summarize the factors on which this evolution depends. As a specific example, we consider the evolution of the medium around a 35Msun star, and the interaction of the shock wave with this medium when the star explodes as a SN. We also discuss the interaction of Type Ia SNe with the ambient medium, especially the formation and growth of hydrodynamic instabilities.

• Abstract: We are studying the interaction of supernova remnants (SNRs) with circumstellar shells, with an emphasis on Type II supernovae (SNe). These supernovae arise from massive progenitor stars (> 8 M_{sun}), which lose mass during their lifetime, primarily in the form of a stellar wind. Often the stellar wind creates a circumstellar bubble surrounded by a dense shell. When the star explodes as a supernova, the resulting shock wave eventually collides with this dense shell. In a recent paper on SN 1987A (Chevalier & Dwarkadas, ApJL, 452, L45) we have shown that from the radio and X-ray emission, one can infer the presence of a high density region interior to the dense circumstellar shell. This can be explained as an HII region photoionized by the flux from the pre-supernova star. Using the Zeus code and assuming spherical symmetry, we have studied the dynamics of the shock wave interacting first with the HII region and then the circumstellar shell in SN 1987A. Collision with the HII region results in a significant deceleration of the shock wave, forming a high-density shocked region that grows with time, and is primarily responsible for the X-ray emission. X-ray emission from the reflected shock may begin to dominate when the forward shock hits the dense circumstellar shell and is considerably slowed down. Simulations are in progress with parameters suited to other remnants such as Cas A and W44. Radio and X-ray images of Cas A show a shell structure, which may result from interaction with a stellar bubble. W44 also shows a double-shell structure that may have been produced by a SN explosion inside a pre-existing wind bubble. The interaction is subject to instabilities that may give rise to filamentary structure.