Transient Phenomena in the High-Redshift Universe: Stellar Mergers and Pulsational Pair-Instability Explosions

Chemical elements, such as Carbon, Oxygen, and Nitrogen, are made within stars. The first stars were made of pristine Hydrogen and Helium only, and they were the first cosmic factories to synthesize advanced chemical elements such as Carbon. The first generation of stars also ended their lives with powerful explosions, spreading complex chemical elements in their nearby environment. This program will carry out advanced numerical simulations to study the explosive end of the first generation of stars to better understand the origin of chemical elements. This project includes a robust outreach initiative designed to engage students in the State of Louisiana through innovative educational opportunities. This program will offer hands-on research experiences to high school and undergraduate students at the LIGO Gravitational Wave Observatory and the University of Crete Institute of Astrophysics, in Greece. This project aims to investigate the transient phenomena of the high-redshift universe, focusing on Pulsational Pair-Instability Supernovae (PPISNe) and massive stellar mergers occurring in low- and zero-metallicity environments. By using cutting-edge hydrodynamic simulations and radiation transport models, the study will explore how these explosive events influence the chemical enrichment of the primordial gas and contribute to the formation of early cosmic structures, such as the first stars, galaxies, and black holes. The project will investigate how the rapid rotation and episodic mass ejections of PPISNe, along with the merger-induced mixing and mass loss in stellar mergers, contribute to cosmic reionization and the creation of the first heavy elements. This program will support the training of a postdoctoral fellow, a graduate student, and several undergraduate students. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.