Stellar multiplicity is ubiquitous in the universe and across the HR diagram. It is therefore a key property in many fields of astrophysics. Past or on-going (e.g, APOGEE, Gaia-ESO, GALAH, etc.) and future (e.g., WEAVE, 4MOST, MOONS, MSE) spectroscopic and photometric (e.g., Corot, Kepler, TESS) surveys allow the community to quickly increase the number of known binary systems. However, a quantum leap is expected with the third data release of the ESA mission Gaia expected for 2022: it should indeed release a rich catalogue of astrometric, eclipsing and spectroscopic stellar systems. There is no doubt that the analysis of these new objects will change our understanding of stellar multiplicity. The aim of this SF2A workshop is to invite the French community interested in stellar systems and to discuss topics/questions such as:
detection and statistical characterization of multiple systems in astrometric/photometric/spectroscopic surveys (including analysis methods based on machine-learning);
stellar multiplicity in astrophysical measurements (distance, photometry, motions, atmospheric parameters, abundances, etc): how to correct, how to model;
fraction of binary stars across the HR diagram and as a function of the metallicity;
formation and evolution of stellar systems (stellar structures, mass transfer (tides, mass loss), orbits, etc.) including new intriguing objects (heartbeat stars, double degenerates, etc.);
stellar systems as planet hosts;
formation and evolution of stellar systems of high multiplicity;
nucleosynthesis of s-, r-, and i-elements in binary stars.
