Detailed Structure and Evolution Modeling of the Tightest Massive Binary Stars

In this PhD thesis, Matthias Fabry takes a deep dive into the detailed structure and evolution of the most massive and tightest binary stars. Massive stars are predominantly born in binary systems, and recent modeling shows that about 40% of them will form a so-called contact binary during their life. In this configuration, both stars share their outer layers, forming peanut-shaped objects. Previously, evolutionary models of such systems used simplified physics and approximations, and were failing to reproduce observed properties of massive contact binaries. In his PhD work, Matthias incorporated tidal deformation and energy transfer into a modern stellar-structure and evolution framework. This culminated in the creation of extensive grids of models spanning all massive stars that would form long-lived contact binaries. In his thesis, Matthias further offers a broad introduction into the history of (computational) stellar evolution, binary stars, and the connection of massive binaries with gravitational-wave astrophysics. Not only do the methods developed here constitute a significant step forward in the detailed modeling of massive contact binaries, they are applicable to many other kinds of binary stars. Nominated for the Springer Theses Prize by KU Leuven.