What event, culminating in a kilonova, is now argued to be the primary source for the bulk of r-process elements?

Answer

The merger of two neutron stars

Recent observations suggest that the merger of two neutron stars provides the perfect crucible for the r-process, leading to the argument that they are the primary source of the bulk of these elements.

What event, culminating in a kilonova, is now argued to be the primary source for the bulk of r-process elements?
Elementastronomystarsupernovanucleosynthesis