Cake Talk by James Gillanders
Kilonovae are the optical counterpart associated with the radioactive decay of an ensemble of freshly synthesised unstable isotopes produced by the rapid neutron-capture process (r-process). The r-process is responsible for synthesising approximately half of all elements beyond the iron peak. Direct observations of r-process nucleosynthesis are limited; to date, the only observed production site remains binary neutron star mergers. These merger systems evolve rapidly and are intrinsically faint compared to virtually all other known extragalactic transients, and so remain elusive to wide-field surveys optimised to search for such events. While there are proposed detections of ~10 kilonova events, only two of these have been observed spectroscopically – AT2017gfo/GRB170817A and AT2023vfi/GRB230307A. In this talk, I will present the spectral observations that exist for kilonovae, with a focus on the heavy r-process element identifications that can be extracted from such observations. Specifically, I will present the results of my recent work to constrain the composition of AT2017gfo, both at early and late times. I will also highlight new work on the exciting JWST spectral observations of AT2023vfi, and what we can extract from these near-infrared, late-time observations.