The beginning of the current century is marked in stellar astrophysics by intensified efforts in understanding evolution of binary (and multiple) systems. Common envelope evolution (CEE) plays a major role in the evolution of many such systems, but its physics remains very poorly understood. The goal of the meeting is to review the latest advances in theoretical studies of CEE and to discuss their confrontation with observations. From the observational side, the meeting is meant to focus chiefly on direct and immediate results of CEE such as transients (including intermediate-luminosity transients or red novae), CEE relation to circumstellar environments of post-AGB objects (including planetary nebulae), and immediate post-CEE stellar remnant properties (such as those apparent in stellar population studies).    

The meeting will run over five days to accommodate a broad range of CEE topics and to give the participants plenty of time for real-time (virtual) discussions (tentatively planned to span at least 1 hour each day in dedicated time slots). Other communication channels will be open and available at all times for astronomers interested in the topic. We wish to encourage vivid interactions that will define paths to progress in this challenging field of astrophysics.

The 2021 virtual meeting is intended as a continuation and extension of the European Astronomical Society (EAS) meeting 2020 session “Common-envelope systems: progenitors, mergers and survivors”. CEPO 2021 is also foreseen to be followed up by an in-situ CEPO meeting in 2023