It has long since been established that observable actinides in the universe originate from the r-process. In 2017, the electromagnetic counterpart to the gravitational wave detection of two merging neutron stars was observed. From the light curve alone it was possible to characterise two ejecta components: one that contains low-Y$_e$ material such as lanthanides and possibly actinides, and a high-Y$_e$ component with low lanthanide abundances.
The dividing characteristic between the two components is the opacity of the material: lanthanides have a $\sim$100 times higher opacity than iron-group material. The opacity of actinides is expected to be on a similar level as that of the lanthanides, or, possibly, even higher. To identify specific elements, spectroscopic information is required. However, so far no clear detection of individual lanthanides or actinides has been made in the electromagnetic counterpart following the neutron star merger AT2017gfo.
A great challenge for spectroscopic modelling of kilonovae using radiative transfer codes is the almost non-existent atomic data currently available for lanthanides and actinides. I will present how converged lanthanide and actinide opacities affect the kilonova spectrum compared to iron-group or light r-process elements. I will then use this collection of atomic data to show how we can use radiative transfer simulations to identify signatures or place constraints on the amount of heavy r-process material synthesized in kilonovae.