We established a multidisciplinary, international network of researchers from Europe, Asia, and South America with expertise and background in both theory and observations and in a variety of disciplines such as astronomy and astrophysics, fluid dynamics, nonlinear physics, molecular physics, astrochemistry, statistics and applied mathematics.
Our research focused on diverse aspects devoted to (i) developing reliable physical descriptions of how the stellar wind emerges, and what kind of structures (disks, rings, arcs, nebulae) it may form, (ii) investigating the influence of pulsations on stellar mass loss and mass eruptions, (iii) studying how the mass lost in each stage of life can alter the star's evolutionary path, (iv) examining the chemical process within the ejected matter, (v) elaborating how the wind material interacts with the interstellar medium, and (vi) exploring the role of companions in altering the evolution of the stars and in shaping the material of the wind and the ejecta.
The work carried out has produced a number of valuable results:
• We have gained new insights into the structure of stellar winds and the mass loss of massive stars in diverse evolutionary states. The newly developed recipes for describing the winds have a major impact on stellar evolution and disk formation (Figure 1).
• We have discovered numerous new ejecta and nebulae (Figure 2) and recorded multiple mass-loss events in yellow hypergiants, requiring a rethinking of the late evolutionary stages of massive stars.
• We have achieved a much better understanding of the instabilities at work in massive supergiants and hypergiants that allow us to elucidate the mass eruptions associated with them and the driving forces for the ejecta (Figure 3).
• We have detected water vapor from the environment of a yellow hypergiant and a B[e] supergiant, which makes these objects unique in their class and requires new interpretation approaches.
• We have spotted strange-mode pulsations and Rossby waves in various supergiants, opening up new dimensions for investigating the interiors of these objects and the impact of large-scale wave dynamics on their winds and mass loss.
• We have developed new analysis techniques to derive binary fractions in diverse massive star populations. The findings for the different populations pose new constraints and challenges to binary evolution in massive stars and to evolutionary connections between the various transition phases.
• We have derived stellar and wind parameters for many objects and determined physical conditions in the environments of numerous evolved massive stars in galaxies of the Local Group, providing means for further studies of metallicity dependence of mass loss events.
• We have developed self-consistent descriptions of the interaction of stellar winds with the interstellar medium. These can be used in both ways: either to predict the shape of the astrosphere and the observable bow shocks, or to infer stellar wind strength and the properties of the interstellar gas using measured quantities from observed bow shock structures.
• We have generated databases of observations and synthetic spectra and provided them to the community for exploitation.
Our results were published in 76 articles (+7 in press) in world renowned journals, 34 conference proceedings (+1 in press), 1 PhD thesis (16 PhD theses are still ongoing) and 10 Master theses. We also published the book "Pulsations along stellar evolution" with 9 chapters written by POEMS team members, and we edited a special issue of the journal Galaxies with title "Theory and Observation of Active B-type Stars".
