Trends in $^{44}$Ti and $^{56}$Ni from Core-Collapse Supernovae

We compare the yields of $^{44}$Ti and $^{56}$Ni produced from post-processing the thermodynamic trajectories from three different core-collapse models with the yields from exponential and power-law trajectories. The peak temperatures and densities achieved in these core-collapse models span several of the distinct nucleosynthesis regions we identify, resulting in different trends in the $^{44}$Ti and $^{56}$Ni yields for different mass elements. The $^{44}$Ti and $^{56}$Ni mass fraction profiles from the exponential and power-law profiles generally explain the tendencies of the post-processed yields, depending on which regions are traversed by the model. We also analyze the influence of specific nuclear reactions on the $^{44}$Ti and $^{56}$Ni abundance evolution. Our analysis suggests that not all $^{44}$Ti need be produced in an $\alpha$-rich freeze-out in core-collapse events, and that reaction rate equilibria in combination with timescale effects for the expansion profile may account for the paucity of $^{44}$Ti observed in supernovae remnants.