During his PhD, Amedeo Romagnolo investigated the evolutionary history of binary black holes, the primary sources of detectable gravitational waves. The research focused on the massive stars that served as the progenitors for these cosmic mergers, addressing the significant uncertainties that currently persist in stellar evolution modeling. Because massive binary systems are both rare and short-lived, capturing their complex physical transitions—from their initial formation to their eventual collapse—remains a significant challenge in the field.
A central contribution of this work involved refining how stellar expansion couples with mass transfer events, a critical factor in determining whether a binary system eventually forms a merging black hole pair. By analyzing these interactions, the research demonstrated that the timing and stability of mass exchange are fundamental to the final architecture of gravitational wave sources. Furthermore, the study re-evaluated the role of stellar winds and their contribution to our knowledge of black hole masses. A key finding revealed that the most massive stars in the local universe do not expand significantly during their evolution, a discovery that challenges traditional assumptions about stellar growth. By providing a clearer link between these internal physical processes and the signals detected by modern observatories, this research advanced the broader understanding of how the fundamental properties of stars dictate the population of black hole mergers within our universe.