Oral Presentation

The Evolution of Population III and Extremely Metal-Poor Binary Stars

Author(s): Sung-Han Tsai (ASIAA/NTU), Ke-Jung Ken (ASIAA)

Presenter: Sung-Han Tsai (ASIAA)

Numerical simulations have now shown that Population III (Pop III) stars can form in binaries and small clusters and that these stars can be in close proximity to each other. If so, they could be subject to binary interactions such as mass exchange that could profoundly alter their evolution, ionizing UV and Lyman-Werner (LW) photon emission, and explosion yields, with important consequences for early cosmological reionization and chemical enrichment. Here we investigate the evolution of Pop III and extremely metal-poor binary stars with the MESA code. We find that interactions ranging from stable mass transfer to common envelope evolution and stellar mergers can occur in these binaries for a wide range of mass ratios and initial separations. However, because these interactions usually occur late in the life of the stars they do not have a large effect on total ionizing and LW UV photon budgets, or hence reionization. However, they could have a much larger effect on early chemical enrichment if mass transfer between the stars promotes or remove them into or out of mass ranges for specific SN types.