Early Solar System r-process Abundances Limit Collapsar Origin

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 _⊙.