K2 Galactic Archaeology Program DR3, final release

We confirm recent indications in the literature of both increased Ba production at late Galactic times as well as significant contributions to r-process enrichment from prompt sources associated with, e.g., core-collapse supernovae. With an eye toward other Galactic archeology applications, we characterize K2 GAP DR3 uncertainties and completeness using injection tests, suggesting that K2 GAP DR3 is largely unbiased in mass/age, with uncertainties of 2.9%(stat.)+/-0.1%(syst.) and 6.7%(stat.)+/-0.3%(syst.) in {kappa}R and {kappa}M for red giant branch stars and 4.7%(stat.)+/-0.3%(syst.) and 11%(stat.)+/-0.9%(syst.) for red clump stars.

We also identify percent-level asteroseismic systematics, which are likely related to the time baseline of the underlying data, and which therefore should be considered in TESS asteroseismic analysis.