IReNA Online Seminar featuring Arthur Choplin (University libre de Bruxelles)

Title : Non-standard neutron capture processes in massive and AGB stars

Abstract : Despite considerable progresses during the last decades, the origin of trans-iron elements is not yet fully understood. These elements are thought to be produced by a variety of nucleosynthetic processes, the main ones being the so called slow (s) and rapid (r) neutron capture processes. An intermediate neutron capture process (i-process) is also thought to occur at neutron densities intermediate between the s- and r-processes. This is supported by the observation of metal-poor stars whose chemical compositions is between the s- and r-processes (the so called r/s-stars). An important challenge is to associate each nucleosynthetic process with its astrophysical source(s). In the first part of the presentation, I will discuss the synthesis of trans-iron elements in low metallicity massive stellar models. In particular, I will show how stellar rotation is expected to alter the synthesis of heavy elements both during the life and explosion of the massive star, and ultimately lead to a material with a chemical composition intermediate between the standard s- and r-processes. In the second part of this presentation, I will focus on the development of the i-process in low-metallicity AGB stars models. In both parts, I will highlight the chemical fingerprint of the discussed nucleosynthetic processes, identify key reaction rates and compare model predictions with observed r/s-stars.