Abstract

Stars are the fundamental building blocks of galaxies, yet many do not evolve in isolation. Instead, they reside in interacting systems—binaries, triples, and higher-order multiples—where stellar interactions can radically alter stellar evolution, trigger dramatic transients, and lead to bursts of gravitational wave emission. The rise of large-scale time-domain surveys has transformed this field, delivering unprecedented samples of stellar systems, electromagnetic transients, and gravitational wave events while simultaneously raising the bar for theoretical modeling.

In this talk, I focus on two key challenges. Firstly, I examine the population of wide post-interaction binaries. Recent observations show that they are overwhelmingly eccentric rather than circular, yet orbital eccentricity has been largely neglected in binary evolution models. What are we missing?

Second, I move beyond the traditional focus on singles and binaries to examine triple systems. They are increasingly recognized as common but remain poorly understood. I highlight recent progress, open questions, and how triples may emerge as key progenitors of future transient discoveries in the era of next-generation surveys.