The article is talking about the r-process, so it’s still supernovas (either core-collapse or more likely neutron star collision) that would have forged these e

The article is talking about the r-process, so it’s still supernovas (either core-collapse or more likely neutron star collision) that would have forged these elements. Ancient or not, a stably burning star isn’t going to synthetize nuclei heavier than iron in non-negligible quantities.