Titanium and Iron in the Cassiopeia A Supernova Remnant

Mixing above the proto-neutron star is believed to play an important role in the supernova engine, and this mixing results in a supernova explosion with asymmetries. Elements produced in the innermost ejecta, e.g., ${}^{56}$Ni and ${}^{44}$Ti, provide a clean probe of this engine. The production of ${}^{44}$Ti is particularly sensitive to the exact production pathway and, by understanding the available pathways, we can use ${}^{44}$Ti to probe the supernova engine. Using thermodynamic trajectories from a three-dimensional supernova explosion model, we review the production of these elements and the structures expected to form under the "convective-engine" paradigm behind supernovae. We compare our results to recent X-ray and $\gamma$-ray observations of the Cassiopeia A supernova remnant.