Modelling of early-stage kilonova ejecta opacity reproducible in laboratory plasmas.

A complete understanding of heavy elements nucleosynthesis is crucial in the framework of the multi-messenger astronomy. This led astrophysicists to investigate the KN (kilonova) emission, a thermal transient strongly dependent on opacity and freshly synthesized elements by the rapid neutron capture process (r-process). Modelling the KN light-curve is challenging: besides the difficulties in modelling the r-process, it requires several inputs, among which opacities are still extremely uncertain. In this context, the PANDORA (Plasma for Astrophysics Nuclear Decay Observation and Radiation for Archaeometry) project aims at measuring, for the first time, plasma opacities from an ECR (Electron Cyclotron Resonance) plasma resembling the theoretical KN ejecta. Thereby, relevant results can be achieved in order to shed light and bridge the gap between theoretical predictions and observations. Here, we present numerical simulations which have been performed to estimate opacity values of a plasma made of heavy metals interesting for the early-stage KN environment. Moreover, numerical estimates of plasma opacity for selected light r-process nuclei will be presented.