I am a PhD candidate at the University of Alberta studying Astrophysics under my supervisor Rodrigo Fernández. My research broadly explores how heavy elements such as gold and uranium are produced. While the big bang set the initial composition of the universe (hydrogen, helium, and small amounts of lithium and deuterium), and elements up to nickel can be created in the cores of massive stars spread throughout the galaxy via supernova explosions at the end of their lives, heavy elements such as gold and uranium are much harder to produce. These heavy elements are predicted to form in violent astrophysical events such as when binary neutron stars, the remnant cores of exploded massive stars, collide with each other. Or in highly rotating supernova explosions called "collapsars", which eject material from around a central black hole.
My research involves computational modelling of binary neutron stars and highly rotating supernova explosions ("collapsars") to explore their viability in explaining heavy element production and predict observational signatures we might be able to detect when observing these transient events.
Neutron stars are the remnant cores of exploded heavy stars and when these stars form in pairs (binary neutron stars) their orbit will decay due to the emission of gravitational waves and eventually the stars will merge with one another. This merger is ideal for the production of heavy elements due to the neutron richness of material ejected in the collision. Seed nuclei expand outward from the merger through this neutron rich material rapidly capturing neutrons to produce heavy unstable nuclei. As those unstable nuclei decay, they power the light signal associated with a BNS merger, the kilonova. My MSc project involved modelling these mergers, looking specifically at some of the fastest ejecta launched from the initial contact of the stars. This fast ejecta is predicted to emit light in the ultaviolet range hours after the merger and could probe fundamental physics such as how matter behaves at the extremely high densities present in neutron stars.
While binary neutron star mergers are a viable production site for heavy elements, they may not be able to explain the level of heavy element enrichment we see in extremely old stars observed in the halo of our galaxy. An astrophysical event that may be able to explain this heavy element enrichment early in our galaxies lifetime are "collapsars". Collapsars are highly rotating massive stars that undergo a supernova explosion at the end of their lifetimes. These stars form a central black hole in their core surrounded by an accretion disk fed by the infalling stellar mantle, and supported by rotation. The outflows from this central black hole - accretion disk system have been proposed as a site for heavy element production. My PhD research involved developing and performing simulations of these explosions, and assessing the viability of this type of supernova explosion for heavy element production.
