Description:

The origin of the heaviest elements in our universe - those produced via the rapid neutron capture process ("r-process") - remains a question of intense debate.  Although the kilonova emission that accompanied GW170817 revealed neutron star mergers to be an important r-process source, several independent observations hint that mergers may not be the only source, particularly at low metallicity.  I will argue that mass-loaded outflows from the accretion disk feeding the newly-formed black hole - that responsible for powering the gamma-ray burst (GRB) jet - was the dominant source of r-process elements in GW170817.  However, broadly similar accretion flows are created in another explosive transient - the collapse of massive rotating stars ("collapsars") which give rise to GRBs of longer duration, and simple estimates show that the integrated r-process yields of collapsars could compete with those of neutron star mergers over the history of the Galaxy.  I will discuss observational tests of whether collapsars produce r-process elements using infrared observations of GRB supernovae, particularly with JWST and the Roman Space Telescope.

 Brian Metzger, Professor, Columbia University, New York

Host: Professor Giacomo Fragione