Speaker
Description
Recent infrared observations obtained with the James Webb Space Telescope (JWST) have significantly advanced the study of kilonovae, delivering the first detailed nebular-phase spectra of AT 2023vfi, only the second kilonova to be observed spectroscopically. The spectra exhibit prominent mid-infrared emission features, some of which have been tentatively linked to r-process elements such as tellurium. With substantially broader wavelength coverage and improved sensitivity compared to the earlier observations of AT 2017gfo, these data place stringent demands on atomic physics input, particularly comprehensive collisional–radiative datasets required to interpret kilonova spectra in the nebular-phase regime.
I present large-scale, calibrated collisional-radiative atomic structure calculations for lanthanide and actinide ions, coupled with nucleosynthesis yields derived from hydrodynamical simulations of binary neutron star mergers, to model late-time kilonova spectra in the non-local thermodynamic equilibrium regime. I explore the role of heavy-ion nebular emission in shaping the mid-infrared features observed in AT 2023vfi, which have not yet been securely attributed to specific elements. I also compare detailed modelling with the currently proposed alternative explanation for these features, namely thermal dust emission. In addition, I will quantify the impact of using detailed collisional-radiative datasets versus widely adopted approximations, both on inferred elemental abundances and on the ability of emission models to reproduce the observed spectra.