Master's Thesis Defense by Sophie Lund Schrøder

Supervisor: Enrico Ramirez-Ruiz
External supervisor: Steen Hannestad
Co-supervisor: Steen Hansen

Title: Winds in Binary Star Systems

Abstract: The majority of massive stars are in binaries, but yet the influence binarity is not fully understood on massive stellar evolution. In this project I have derived relations for changes in binary orbits, when one of the stars has a wind. I have parametetrized wind acceleration from line driven winds from the original Castor, Abbott and Klein formalism, to form an easily acceleration scjeme implemented in the hydrodynamic code Athena++. The setup is used to run simulations with different wind velocity, mass ratio and wind velocity slope. The gravity of the companion focuses the wind material in a wake spiraling around the binary. The torque of the wind on the binary is measured as a function of wind velocity. The drag on the binary occurs in a more efficient manner by a factor of 1.5 than in the standard Bondi Hoyle formalism. I also see a variation with mass ratio, that is not accounted for yet. Finally, I see a small relation between torque on the binary and the slope of wind velocity.

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