Kilonovae across the nuclear physics landscape: The impact of nuclear physics uncertainties on r-process-powered emission

TL;DR

This paper investigates how uncertainties in nuclear physics affect the modeling and interpretation of kilonova emissions from neutron star mergers, highlighting the diversity and complexity of observable signals.

Contribution

It provides a detailed analysis of the impact of nuclear physics uncertainties on kilonova light curves and offers insights into interpreting observational data.

Findings

Kilonova brightness can vary by over an order of magnitude due to nuclear physics uncertainties.

Light curve shapes and colors are highly variable and sometimes counterintuitive.

Nuclear physics uncertainties significantly complicate the inference of merger outflow properties.

Abstract

Merging neutron stars produce "kilonovae"---electromagnetic transients powered by the decay of unstable nuclei synthesized via rapid neutron capture (the r-process) in material that is gravitationally unbound during inspiral and coalescence. Kilonova emission, if accurately interpreted, can be used to characterize the masses and compositions of merger-driven outflows, helping to resolve a long-standing debate about the origins of r-process material in the Universe. We explore how the uncertain properties of nuclei involved in the r-process complicate the inference of outflow properties from kilonova observations. Using r-process simulations, we show how nuclear physics uncertainties impact predictions of radioactive heating and element synthesis. For a set of models that span a large range in both predicted heating and final abundances, we carry out detailed numerical calculations of decay product thermalization and radiation transport in a kilonova ejecta with a fixed mass and density profile. The light curves associated with our models exhibit great diversity in their luminosities, with peak brightness varying by more than an order of magnitude. We also find variability in the shape of the kilonova light curves and their color, which in some cases runs counter to the expectation that increasing levels of lanthanide and/or actinide enrichment will be correlated with longer, dimmer, redder emission.