Turbulent and Explosive Lives of Massive Stars

ongoing

Stars are the basic building blocks of the visible Universe. Understanding how they transformed the pristine Universe into the one we live in today is at the heart of astrophysical research and vital for many areas in astrophysics. Massive stars, in particular, are cosmic powerhouses because of their radiative, mechanical and chemical feedback from stellar winds and supernova explosions. Thanks to new telescopes and observatories, massive star research is entering a golden era, as exemplified by transient surveys and the dawn of gravitational-wave astronomy. Yet, our understanding of the lives and final fates of massive stars is incomplete. Binary stars are of particular importance because the vast majority of all massive stars will exchange mass with a companion during their life, thereby completely changing their evolution and final fates. About 25% of massive stars are even thought to merge. The merger phase is largely unexplored and the consequences of binary mass exchange for supernovae are poorly understood. To remedy this situation, I propose to build the essential theoretical framework to help understand massive stars. My group will conduct the first 3D magnetohydrodynamical simulations of stellar mergers, develop merger prescriptions for stellar evolution codes, compute grids of massive single and binary stars that cover all relevant phases, and build the required statistical methods to compare models with observations. We will unravel whether merging can explain the origin of strong magnetic fields in 10% of massive stars and thereby also that of the strongest magnetic fields in the Universe, namely those of magnetars. Moreover, we will study the asteroseismic properties of mergers and will understand how binary mass exchange affects pre-SN structures and hence the explosions of massive stars. In this way, we will push the frontiers of massive star research and help to approach a truly comprehensive picture of the lives and final fates of massive stars.