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

In the framework of the multi-messenger astronomy, for a complete understanding of the heavy elements nucleosynthesis, investigation of the kilo- nova (KN) emission is crucial. The KN is a thermal transient signal following gravitational-wave events from the coalescence of compact objects. Modelling the KN light-curve is challenging: besides the difficulties in modelling the r-process synthesised elements, it requires several inputs, among which plasma ejecta opacity is still extremely uncertain. In this context, the PANDORA project aims at measuring, for the first time, opacities of a plasma resembling the plasma ejecta through which KN diffuses. In view of that, we present numerical estimates of argon plasma opacity perturbed by an external radiation flux under non local thermodynamic equilibrium. Simulations performed serve as demonstrator for further metallic elements, and their results underline that both thermodynamic parameters and radiation could impact on the opacity of the plasma.