Abstract

Contributed Talk - Splinter GWAstronomy

Thursday, 18 September 2025, 16:15

Calibrated Nebular Emission Lines of Lanthanide Ions for NLTE Kilonova Modelling

Andreas Flörs, Ricardo Ferreira Da Silva, Luke Shingles, Oliver Just, Gabriel Martínez-Pinedo
GSI Helmholtzzentrum für Schwerionenforschung

The detection of multiple neutron star mergers has highlighted the urgent need to refine our understanding of nuclear properties, atomic structure, and radiative transfer. Despite progress, significant uncertainties remain in opacity estimates, complicating the identification of r-process elements. JWST observations have revealed numerous infrared spectral features, some of which may arise from forbidden line emission by lanthanide ions, known for their complex atomic structures. We present calibrated atomic structure calculations for all singly and doubly ionised lanthanides and use them to compute forbidden transitions that dominate kilonova cooling from around one week post-merger. These transitions are critical for accurate non-LTE radiative transfer modelling. By incorporating them into radiative transfer simulations, we predict nebular-phase spectra (>1 week after merger) for comparison with JWST data. Analysing both dynamical and post-merger ejecta from relativistic simulations, we find that nebular spectra display spatially distinct features, enabling identification of individual r-process elements.