Where Was the Iron Synthesized in Cassiopeia A?

We investigate the properties of Fe-rich knots on the east limb of the Cassiopeia A supernova remnant using observations with Chandra /ACIS and analysis methods developed in a companion paper. We use the fitted ionization age and electron temperature of the knots to constrain the ejecta density profile and the Lagrangian mass coordinates of the knots. Fe-rich knots that also have strong emission from Si, S, Ar, and Ca are clustered around mass coordinates q ≃ 0.35-0.4 in the shocked ejecta; for ejecta mass 2 M ☉ , this places the knots 0.7-0.8 M ☉ out from the center (or 2-2.1 M ☉ , allowing for a 1.3 M ☉ compact object). We also find an Fe clump that is evidently devoid of line emission from lower mass elements, as would be expected if it were the product of α-rich freezeout; the mass coordinate of this clump is similar to those of the other Fe knots.