Supernova and Supernova Remnant Studies

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

Professor Chevalier and collaborators will undertake four projects that are expected to greatly improve our understanding of the late evolution of massive stars and how/why they end their lives in supernovae. Key to three of these efforts is the study of how supernova ejecta interacts with material shed from stars before the explosion. (1) Type IIn supernovae, with relatively narrow emission lines, represent supernova interaction with up to several solar masses of clumpy circumstellar material that was lost shortly before the explosion. New models for radio and infrared emission, together with inferences from other multiwavelength data, will be combined with hydrodynamic models to better constrain the mass loss, which apparently is episodic, and to place the supernovae in the context of massive star evolution. A revision of the standard view of the final evolution of massive stars may well be required as a result of this work. (2) Type IIP (plateau light curve) supernovae have the highest occurrence rate of core collapse supernovae, but are curiously not well represented among young supernova remnants. The hypothesis that this is due to a low-density surrounding, as expected for stars in the progenitor mass range, will be evaluated through hydrodynamic simulations. The results will be compared to observations of a number of young remnants, including the Crab Nebula. (3) Hydrodynamic models, together with calculations of particle evolution and nonthermal X-ray and radio emission, will be used to set constraints on the mass loss density around normal Type Ia supernovae. The limits are expected to be the strongest for constraining the progenitor system. A fourth project will examine nonradial instability in the late phases of massive star core collapse, which may be a crucial part of the supernova explosion mechanism. A linear analysis of the instability will be used to settle a discrepancy in previous studies and to investigate the physical mechanism for the instability. These projects have broad implications for astrophysics in that they are relevant to the late evolution of massive stars, the return of heavy elements to the interstellar medium, and physical processes at high energy densities. The research will also build and maintain ties between the University of Virginia and Stockholm Observatory. The results will be broadly disseminated at conferences and colloquia. A graduate student and an undergraduate student will be involved in carrying out the research and will learn techniques used in theoretical astrophysics. Finally, the topic of exploding stars is one that captures the public imagination and the research results will be integrated into undergraduate courses and public lectures.