Kilonovae and the cosmic origin of r-process elements: atomic structure and opacities

Project title: Kilonovae and the cosmic origin of r-process elements: atomic structure and opacities
Main applicant: Jon Grumer, Division of Astronomy and Space Physics
Grant amount: 3 600 000 SEK for the period 2021-2024

The cosmic origin of elements beyond iron in the periodic table is a long-standing puzzle. As such, one of the main astrophysical highlights of the last decade is, without doubt, the indication of rapid neutron capture (r- process) nucleosynthesis of heavy elements in the kilonova (KN) ejecta following the neutron star (NS) merger gravitational-wave event detected in 2017. The analysis of such an event requires information on largely uncharted atomic species as input to the spectral modeling of the ejecta.

This project aims to tackle the lack of atomic data for the complex r-process elements with state-of-the-art atomic structure methods, determine opacity tables, and finally, combine this with a novel KN radiative transfer method to analyze the current and future observations. Reliable data for r-process elements is crucial, not only to allow for their direct identification in KN spectra, but also to determine fundamental parameters such as temperature and expansion velocity of the ejecta itself, and ultimately of the progenitor binary NS system.

The proposed research programme includes two main work packages: WP1 covers systematic calculations of fundamental atomic data using the best available methods, and from this data, WP2 deals with the construction of opacity tables for the community to use in e.g. light curve models, and also the implementation of the produced energy levels and line lists in a state-of-the-art non-local thermal equilibrium spectral synthesis ejecta model.