# Early Solar System $r$-process Abundances Limit Collapsar Origin

## TL;DR

This study uses simulations and Solar System abundance data to show that collapsars are unlikely the main source of $r$-process elements, favoring neutron star mergers instead.

## Contribution

It provides quantitative constraints on the contribution of collapsars to $r$-process element production in the early Solar System.

## Key findings

- Collapsars contribute less than 20% to Solar $r$-process abundances.
- $r$-process ejecta from collapsars is limited to less than 10% of neutron star merger ejecta.
- Neutron star mergers are the dominant source of $r$-process elements in the Solar System.

## Abstract

Heavy elements produced exclusively through rapid neutron capture (the '$r$-process') originate from violent cosmic explosions. While neutron star mergers are the primary candidates, another plausible production site are 'collapsars'---collapsing massive stars that form a black hole with an accretion disk. Here we show that collapsars are too rare to be the prime origin of $r$-process elements in the Solar System. By comparing numerical simulations with the early Solar System abundances of actinides produced exclusively through the $r$-process, we exclude higher than 20% contribution from collapsars with 90% confidence. We additionally limit $r$-process ejecta masses from collapsars to less than 10% of the ejecta mass from neutron star mergers, about $10^{-2}$M$_\odot$.