  The astrophysical production site of the heaviest elements in the universe
remains a mystery. Incorporating heavy element signatures of metal-poor,
$r$-process enhanced stars into theoretical studies of $r$-process production
can offer crucial constraints on the origin of heavy elements. In this study,
we introduce and apply the "Actinide-Dilution with Matching" model to a variety
of stellar groups ranging from actinide-deficient to actinide-enhanced to
empirically characterize $r$-process ejecta mass as a function of electron
fraction. We find that actinide-boost stars do not indicate the need for a
unique and separate $r$-process progenitor. Rather, small variations of neutron
richness within the same type of $r$-process event can account for all observed
levels of actinide enhancements. The very low-$Y_e$, fission-cycling ejecta of
an $r$-process event need only constitute 10-30% of the total ejecta mass to
accommodate most actinide abundances of metal-poor stars. We find that our
empirical $Y_e$ distributions of ejecta are similar to those inferred from
studies of GW170817 mass ejecta ratios, which is consistent with neutron-star
mergers being a source of the heavy elements in metal-poor, $r$-process
enhanced stars.
