Modeling the Light Curve of HD 222925's Progenitor Kilonova

Abstract

The leading theory for heavy element nucleosynthesis is that a majority of isotopes heavier than iron are formed in neutron star mergers (NSMs), visible through the kilonovae that proceed them. In this work, we derive the potential kilonova light curve associated with the elemental abundances of the “gold standard” metal-poor star HD 222925, which is thought to be enriched by a single NSM. Previous work explores which initial kilonova conditions best match the elemental abundances in HD 222925 and finds two main solutions: either the ejecta is highly constrained, or the underlying nuclear microphysics model is incomplete. We construct the light curves for these two cases in hopes of using kilonova to break this degeneracy. We find that our merger models produce light curves that are observationally too alike to robustly distinguish between the two valid models, offering little hope for constraining kilonova ejecta or the behavior of neutron-rich nuclei.