Ricardo Vaca
FCUP

Abstract
Historically, globular clusters (GCs) have been thought of as simple stellar populations and, due to their old age and low metallicity, are excellent tracers of the evolution of their parent galaxy. However, studies have shown that the stars belonging to individual clusters can be divided into different populations with different chemical abundances while maintaining a very small age difference. Through these observations, studies have found that individual stars of almost all GCs show variations in the abundances of certain elements, such as He, Na, O, N, C, Al, and sometimes Mg . These variations are present even in main sequence stars, suggesting that they are present during the formation of the star rather than being a product of stellar evolution. Despite decades of effort, no satisfactory explanation has yet been found to describe the mechanism responsible for the observed chemical patterns. Finding the origin of these variations remains a major challenge in stellar and galactic astrophysics, and the origin of this phenomenon is still an open question. We tested the three most popular models proposed for the origin of this phenomenon: asymptotic giant branch stars (AGBs), high-mass interacting binaries (IBs), and fast rotating massive stars (FRMSs) in twenty-six clusters (increasing the number of clusters in previous studies by more than a factor of three) to see if any of them can replicate the observations. We also included the study of the abundances of N, C, Mg, and Al, extending previous studies that mainly focused on the abundances of He, O, and Na. In addition, we constructed an empirical model to test whether one could explain the chemical signatures of the "enriched" population of GC stars with a fixed source and dilution process based on empirical data.

2024 December 04, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Classroom)
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