On the Geometry of the High-Velocity Ejecta of the Peculiar Type Ia Supernova 2000cx

Abstract

High-velocity features in Type Ia supernova spectra provide a way to probe the outer layers of these explosions. The maximum-light spectra of the unique Type Ia supernova 2000cx exhibit interesting Ca II features with high-velocity components. The infrared triplet absorption is quadruply notched, while the H&K absorption is wide and flat. Stimulated by a three-dimensional interpretation of similar Ca II features in another Type Ia supernova (SN 2001el, Kasen et al. 2003), we present alternative spherically symmetric and three-dimensional ejecta models to fit the high-velocity (v > 16,000 km/s) Ca II features of SN 2000cx. We also present simple estimates of the high-velocity ejecta mass for a few trial compositions and discuss their implications for explosion modelling.