Metal-Rich Ejecta Rings in Puppis A: Kinematics and Composition

A structure of highly unusual composition and kinematic properties exists near the center of the Galactic oxygen-rich supernova remnant Puppis A. Our WiFeS integral field observations indicate that the structure (referred to as 'the Swirl') consists of multiple rings of high velocity ($\sim$ -1300 km/s) material around 1 pc across. The rings occur at nearly quantized velocity intervals of -350, -750 and -1300 km/s and consist of metal-rich material of highly variable composition. Modeling the spectra at several locations in the Swirl with radiative shock models, we find shock speeds $\sim$ 100-150 km/s and abundances of C, O, and Ne ranging from 10 times solar in the inner rings to nearly negligible levels in the outside ring, where instead the N abundance reaches 25 times Solar. The rings could possibly have originated from interaction of the supernova shock from one member of a massive binary with the outer atmosphere of the other member.