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Session 39 - Supernovae.
Display session, Thursday, January 08
We examine the relation between presupernova stellar structure and the distribution of ejecta in core-collapse supernovae of types II and Ib. We develop a simple yet accurate analytical formula for the velocity of the initial forward shock that traverses the stellar envelope. For material that does not later experience a strong reverse shock, the entropy deposited by this forward shock persists into the final, freely-expanding state. We demonstrate that the final density distribution can be approximated with simple models for the final pressure distribution. Using these models we survey the ejecta of polytropic stellar envelopes. Our results indicate that the distribution of a star's ejecta depends on the nature of its outer envelope (radiative or convective) and on its outer envelope and ejected masses, relative to its total mass.
More accurate models are developed to describe the highest-velocity ejecta. We show that the dynamics of shock acceleration and the subsequent rarefaction of the outermost mass shells limit to common forms for both radiative and convective envelopes. Using the relation between the final and post-shock velocities of this material, we present formulae for its final distribution. These formulae limit to the well-known planar, self-similar solutions for mass shells approaching the stellar surface. However, the assumption of adiabatic flow breaks down for these shells, so this planar limit need not be attained. Our models will be useful for studies of the circumstellar or interstellar interactions and light curves of core-collapse supernovae.
Program listing for Thursday