Periodic Reporting for period 2 - POEMS (Physics of Extreme Massive Stars)
Periodo di rendicontazione: 2022-06-01 al 2024-08-31
Massive stars are powerful cosmic engines. Throughout their life-time they enrich the environment with huge amounts of energy and with chemically processed material. The energy released is so powerful that it can trigger the formation of new generations of stars and planets, and the chemical elements produced inside these stars, and released to their environment via winds and eruptions, are the building blocks of all life as we know it on Earth.
Despite the importance of massive stars for cosmic evolution, their aging process from the cradle up to their death in spectacular supernova explosions is most uncertain. This is due to the lack of precise knowledge of the physical mechanisms behind mass eruptions that occasionally occur during various late phases in the evolution of massive stars, and due to the high uncertainties in reliable values of the total amount of mass the star loses during each epoch of its life.
With this project, we have succeeded in eliminating some of these uncertainties, allowing us to make reliable predictions about the evolution and fate of massive stars. The acquired knowledge will boost our understanding of physical and chemical processes taking place in the universe and their mutual interactions, which have relevance not only on galactic and intergalactic scales, but also on Earth and in every-day life. The results of our research will make the society more aware of our current position and our transiency in the universe. The new methodologies of calculation, image processing, data management, numerical methods, etc., created by our team can be used according to the needs of business, industry and for teaching at different levels of education. The newly acquired knowledge has the potential to drive the development of new devices to carry out future research projects and of new technologies of which society as a whole will benefit.
Despite the importance of massive stars for cosmic evolution, their aging process from the cradle up to their death in spectacular supernova explosions is most uncertain. This is due to the lack of precise knowledge of the physical mechanisms behind mass eruptions that occasionally occur during various late phases in the evolution of massive stars, and due to the high uncertainties in reliable values of the total amount of mass the star loses during each epoch of its life.
With this project, we have succeeded in eliminating some of these uncertainties, allowing us to make reliable predictions about the evolution and fate of massive stars. The acquired knowledge will boost our understanding of physical and chemical processes taking place in the universe and their mutual interactions, which have relevance not only on galactic and intergalactic scales, but also on Earth and in every-day life. The results of our research will make the society more aware of our current position and our transiency in the universe. The new methodologies of calculation, image processing, data management, numerical methods, etc., created by our team can be used according to the needs of business, industry and for teaching at different levels of education. The newly acquired knowledge has the potential to drive the development of new devices to carry out future research projects and of new technologies of which society as a whole will benefit.
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".
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".
The research carried out by our team is at the forefront of science in several research areas, such as stellar wind modeling, modeling of oscillations in extreme massive stars, and observing and modeling the environments of massive stars in transition phases. Our team developed cutting-edge models and software and was extremely efficient in getting assigned observing time with most modern observing facilities. A particularly important role play hereby the multiple, unique facilities at Gemini Observatory which our team used intensively. Access to these facilities is granted solely to our South-American partners, and especially our Argentinian colleagues are at the forefront in obtaining observing time with them. This makes the collaboration between Europe and South-America extremely beneficial and fruitful and allowed us to collect the best possible data (and often the first of their kind) that were shared among POEMS members, placing our team ahead. With the final results from POEMS we expect to maintain and consolidate this leading position in massive star research.
POEMS helped to enhance the Master and PhD theses of the students and to promote the obtaining of their degrees. Students and young researchers further benefited from the exchange visits within the large international collaboration that allowed them to set-up and tighten their scientific network, and the acquired knowledge and training they received helped them for being promoted to new academic positions. Also, young female participants from Azerbaijan received high recognition in their home country for their participation in POEMS.
Moreover, POEMS members achieved recognition by policy makers for their engagement in promoting and consolidating cooperation in science, technology and innovation, for their efforts in training human resources, and for the huge impact of their scientific work and results at the international level.
POEMS helped to enhance the Master and PhD theses of the students and to promote the obtaining of their degrees. Students and young researchers further benefited from the exchange visits within the large international collaboration that allowed them to set-up and tighten their scientific network, and the acquired knowledge and training they received helped them for being promoted to new academic positions. Also, young female participants from Azerbaijan received high recognition in their home country for their participation in POEMS.
Moreover, POEMS members achieved recognition by policy makers for their engagement in promoting and consolidating cooperation in science, technology and innovation, for their efforts in training human resources, and for the huge impact of their scientific work and results at the international level.