A new site for heavy element nucleosynthesis

UTK Colloquium

Invited presentation on 04/2026

The origin of the heaviest elements in the universe remains one of the most exciting open questions in nuclear astrophysics. Recently, kilonova-like emissions following long-duration gamma-ray bursts (GRBs) have been interpreted as arising from neutron star mergers. In this talk, I will explore a compelling alternative: the jet of a collapsing massive star. First, I will introduce a novel mechanism showing how collapsing massive stars can effectively manufacture their own neutrons. Even if the surrounding stellar material is initially devoid of neutrons, the extreme, high-flux photon environment of a jet can generate them in situ when photons interact with protons. This sudden inundation of neutrons transforms the region into an ideal nursery for heavy element creation. Second, I will ground this theory in recent observations. I will demonstrate that our jet model accurately reproduces the optical and infrared light curves of these events using only a "weak" r-process component. Strikingly, this matches the data without requiring the lanthanide-rich material traditionally assumed to drive the red component of such transients. We conclude that collapsars are a powerful engine for heavy element synthesis, reshaping our understanding of where and how the universe forges its most extreme materials.