%0 Generic
%A Ohlmann, Sebastian Thomas
%D 2016
%F heidok:21513
%R 10.11588/heidok.00021513
%T Hydrodynamics of the Common Envelope Phase in Binary Stellar Evolution
%U https://archiv.ub.uni-heidelberg.de/volltextserver/21513/
%X The common envelope (CE) phase is critical for the formation of close binary stars with at least  one compact star. During this phase, a giant star engulfs its companion, which spirals into the  giant’s envelope. The envelope is ejected and a close binary system results. The ejection mechanism  is unknown and predicting the final state of the system is a long-standing problem in binary stellar  evolution.  This work establishes the moving-mesh hydrodynamics code AREPO as a new approach to  model CE phases, going beyond the current state of the art. Envelopes of giants are stabilized as  initial conditions. Then, the first CE simulation on a moving mesh demonstrates the occurence of  dynamical instabilities. AREPO’s refinement capabilities allow high resolution around the point  masses representing the core of the giant and the companion; this is essential for convergence.  The first magnetohydrodynamic CE simulations show strong field amplifications possibly due to  the magnetorotational instability. Analyzing the transport of angular momentum and energy yields  no significant contribution by magnetic fields; main drivers are gravitational torques and shocks.  Including the ionization state of the gas increases the unbound mass by releasing recombination  energy, but still fails to completely eject the envelope during the simulation.