Research Division Seminar
The evolution and outcomes of the first massive stars in the Universe
Extremely metal-poor or zero-metallicity very massive stars, with initial mass in the range 100 ≲ Mi/M⊙ ≲ 1000, have a broad astrophysical impact. Understanding how these population III stars evolve and die has implications for several key questions, including the nature of energetic transients such as pair-instability supernovæ and gamma-ray bursts, the source of extreme ionizing UV-radiation fields at high redshifts, the earliest chemical enrichment of their host galaxies and the rates of gravitational-wave emission from merging black holes among others. There are not many models in literature that follow the evolution of these population III stars, and even less so that reach the phases where the production of electron-positron pairs alter the stability of the whole star. We present new evolutionary models of very massive primordial stars, with initial masses ranging from 100 M☉ to 1000 M☉, that extend from the main sequence until the onset of dynamical instability. We focus on the final outcome of the models and associated compact remnants. Stars that avoid the pair-instability supernova channel, should produce black holes with masses ranging from ~ 40 M☉ to ~ 1000 M☉. In particular, stars with initial masses of about 100 M☉ could leave black holes of ≃ 85-90 M☉, values consistent with the estimated primary black hole mass of the GW190521 merger event. Overall, these results may contribute to explain future data from next-generation gravitational-wave detectors, such as the Einstein Telescope and Cosmic Explorer, which will have access to as-yet unexplored BH mass range of ~ 10^2-10^4 M☉ in the early universe.