From Central Engine to Bipolar Outflow: Binaries, MHD and the Evolution of Planetary Nebulae

点击翻译按钮获取中文摘要

Dr. Frank and his team study the late stages of stellar evolution for low and intermediate mass stars, when these stars evolve into proto planetary nebulae (PPN) and planetary nebulae (PN) and lose large fractions of their mass to the interstellar medium. Proto planetary nebulae often show collimated energetic outflows that cannot be explained by radiative driving and launching or collimation of proto planetary nebulae is not well understood. The team developed a new paradigm in which binaries and magneto-hydrodynamic processes are responsible for the majority of PPN and PN. The researchers established the potential efficacy of magneto-centrifugal launching processes in PPN and PN and found pathways by which binary companions create conditions for magneto-hydrodynamic launching including the efficacy of dynamo processes. Here the work focuses on several topics: Simulations of the pathways for accretion disk formation in PPN and PN binary systems by wind capture; common envelope evolution in the context of PPN/PN to understand when disks form after ejection of the bulk stellar envelope; and the propagation of magnetically dominated magnetic tower jets which are likely resulting in the disks. The magneto-hydrodynamic outflow simulations are compared to laboratory astrophysics experiments at Imperial College in London that generate hyper-fast mode, radiative magnetic plasma outflows and jets. All computations use the Adaptive Mesh Refinement magneto-hydrodynamic, multiphysics code AstroBEAR built at the University of Rochester. The parallel AMR engine of the AstroBEAR code will be redesigned to allow it to reach towards Petascale computing on massively parallel platforms. This work is relevant to other research areas where collimated outflows from a central gravitating source are observed. The project provides student and postdoc training in computational astrophysics and fosters closer connections between astronomers and plasma experimentalists.