The making of the heaviest elements in the Universe

About half the elements heavier than iron in the Universe are created in the rapid neutron-capture (r)process. Yet, more than 60-years after its theoretical prediction, the astrophysical site of this process is still debated.

However, in 2016 a small team of international experts, the R-Process Alliance (RPA), initiated a successful search to uncover bright metal-poor halo stars with r-process element enhancements.

The chemical composition of these old stars, mapped through detailed abundance analysis, is a direct fingerprint of the elements produced in the stellar generation before them.

To date, the RPA has collected spectra of ~2000 stars, and this project aims to use this extensive new dataset to explore the nature and astrophysical site of the r-process.

Specifically, abundances for 12 light r-process elements in the region from Ga to Sn can be derived from the highly r-process enhanced stars in the sample, facilitating an in-depth investigation of this largely unexplored region of the r-process. Similarly, abundances of 31 heavy elements from Ba to U can be derived.

In collaboration with Dr.

Lind, 3D non-LTE models for the neutron-capture elements will be developed, ensuring accurate abundances are derived from the stars. Furthermore, using the neutron star nucleosynthesis models of Prof.

Rosswog we will investigate if this, the only observed site of r-process element production, can account for all the r-process elements in the Universe or multiple sites are required.