Common envelope evolution (CEE) is a crucial phase in stellar binary evolution, as it is responsible for the formation of many of the most exciting systems in astrophysics, including sources of gravitational waves. Despite its importance, several unanswered questions hamper the urgently needed progress in this field: What systems enter CEE? What happens during CEE? How the CEE remnants evolve? 

Recently, a new type of astrophysical transients called luminous red novae (LRNe) has emerged as direct observational evidence of the dynamical ejection of the CE in binaries. My work on their progenitor systems and their late-time evolution has shown their potential to study the initial and final state of binary systems entering CEE. The imminent start of operations of the large transient surveys BlackGEM and LSST provides a unique opportunity to bring CEE observational studies to the next level with LRNe population studies. 

This project aims to study the different stages of CEE in massive binaries using observations of extragalactic LRNe. The sample will contain ~30 transients within 15 Mpc from massive binary progenitors with HST archival data. My team will use a novel transient selection strategy to identify a fraction of these LRNe years before their main outburst and study the extensive mass loss leading to coalescence. Novel observational and modeling techniques in optical and infrared wavelengths will allow me to derive the energetics, chemistry, dust content, and geometry of the outbursts. 

This project will provide the so-needed evidence of the physical processes that occur before, during, and after the ejection of the CE in massive binary systems, the characteristics of their progenitors, and their rate in our Local Universe. This will in turn have a fundamental impact on several fields of astrophysics such as binary population synthesis, simulations of CEE, and understanding of mass transfer in the progenitor systems of gravitational wave sources.