Martina Koppitz

Master Student

Field of Interests

I am highly interested in Nuclear Astrophysics and Astroparticle Physics. Especially the early stages of our universe caught my interest. Shortly after the Big Bang, only hydrogen and helium (and traces of lithium and beryllium) were able to form. The rest of the elements as we know formed during the next millions and billions of years through stars. Nuclei up to iron formed via nuclear fusion inside them, heavier elements formed in supernovae explosions or neutron star mergers. The first generation of stars, called Pop III stars, started to form around 200 million years after the Big Bang. Although we are not able to observe them with our current generation of instruments, we can instead search for the most metal poor stars. Assuming they were enriched with the ashes of these first generation supernovae, we can try to reconcile the measured elemental abundances with the theoretical nucleosynthetic yields of Pop III supernovae to infer their masses.

In my master’s thesis I will investigate the nucleosynthetic yields of a Pop III Core-Collapse Supernovae. For this, I will run a simulation in 3D, using the Eulerian adaptive mesh refinement (AMR) hydrodynamics code CASTRO. The necessary stellar progenitor model was already evolved in a stellar evolution code, all the way from the start of central hydrogen burning on the main sequence until the onset of collapse of their iron cores.  This object now carries all the information about the elemental abundances created inside the star through stellar nucleosynthesis during its life and its arrangement in shells around the iron core. This 1D model is mapped on the 3D CASTRO grid using a conservative mapping scheme to ensure conservation of mass and energy. An explosion is triggered by the deposition of linear momentum. I will model fallback, mixing and explosive nuclear burning which regulate the nucleosynthetic yields and deduce the chemical yields of the elements ejected by the supernova. Knowing such detailed Pop III supernovae nucleosynthetic yields not only helps us constrain properties of the first stars, but also to constrain at what time the first habitable worlds in our universe may have formed.