Seminar

Studying the common envelope ejection in binary stars with luminous red novae (LRNe)

By
Nadia Blagorodnova
Date
Place
Zoom
seminar ICCUB
Interactions between binary stars shape the Universe in multiple ways, creating sources of gravitational waves, progenitors of stripped core-collapse and type Ia supernovae, X-ray binaries and cataclysmic variables among others. One of the most critical phases in this interaction is the common envelope evolution. In this phase, unstable mass transfer from one star to another can lead to the formation of a shared gaseous shell where both stars orbit: the common envelope. The end of this phase is marked by the quick spiral-in of the secondary star towards its companion, leading to violent interactions between the components: the whole, or part of the binary's common envelope may get ejected, leaving a more compact binary, or a coalesced star. Despite its importance, the phase of common envelope evolution is currently one of the least understood, due to the many theoretical and observational challenges. Within the last decade, a new type of astrophysical transients named luminous red novae (LRNe) have emerged as a promising observational approach to witness in real time the ejection of the common envelope in close binary stars. Observations of such transients, along with the study of their progenitor systems and their remnants at later times already delivered valuable results for our understanding of the physics at play during this phase. In my talk, I will review the lessons that observational studies of LRNe have taught us about their progenitor's binary evolution scenarios, the mechanisms leading to the final dynamical instability and mass ejection, and their link to post-CE stellar populations and transients. I will also outline the main challenges in this field, and how these can be addressed by future large time-domain surveys.