Supernova Shock Wave and Radiative Interactions

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

Supernovae (SNe) are explosions that end the lives of massive stars. They are important to study since supernovae seed the galaxy with atomic elements made in the star and in the explosion, and they help astronomers to understand how stars evolve and die. One of the ways astronomers study supernovae is by observing how the matter ejected in the SNe interacts with the gaseous material surrounding the star, producing a shock wave. In order to help to interpret such observations, a research team at the University of Virginia will carry out a program to investigate the interaction of a supernova with a dense circumstellar medium. Their study will include hydrodynamic computer simulations, modeling of energy transfer in the form of electromagnetic radiation, and calculations of physical conditions in the shock. By better defining the nature of the circumstellar media involved in these events, this research seeks to fill gaps in stellar evolution theory. The principal investigator will give annual public lectures at the McCormick Observatory, near the university, as well as talks for elderly persons given at accessible sites. A graduate student and an undergraduate student will be involved in the research and will learn techniques used in theoretical astrophysics, as well as ways of approaching open questions. The goal of the project is to investigate the interaction of a supernova with a dense, possibly optically thick, circumstellar medium. The physical conditions are more extreme than ordinarily encountered in supernova interactions and the structure of the mass loss region is probably complex. The researchers will develop diagnostics for the conditions in and structure of the interaction. Specific topics that will be addressed include the shock wave structure and hydrodynamic instabilities when cooling is important, consistent models for X-ray and ultraviolet/optical shock emission, pre-shock ionization and emission, nonthermal particles and radio emission and absorption, and infrared emission from the radiative heating of dust. The models will be compared to multiwavelength observations, from radio to X-rays. The research will relate the findings for observed interacting supernovae to plausible mechanisms for driving the pre-supernova mass loss. Supernovae that have narrow line characteristics are inferred to have a dense, slow moving circumstellar medium. These characteristics are observed over a broad range of supernova types, including those with and without hydrogen lines, superluminous supernovae, supernovae with Type Ia characteristics, and possible low energy supernovae. For these events, neither the mechanism driving the mass loss nor the timing with the supernova is understood, although narrow line supernovae make up about 9% of Type II supernovae. By better defining the nature of the circumstellar media involved in these events, this research seeks to fill gaps in stellar evolution theory. In addition, aspects of the physical processes in dense media should be more broadly applicable, for example to the dense media in active galactic nuclei. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.