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

从中央引擎到双极外流：双星、MHD 和行星状星云的演化

• 批准号: 1109285
• 负责人: Adam Frank
• 金额: $ 40.6万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1109285&HistoricalAwards=false
• 关键词: Central; Engine; Bipolar; Outflow; Binaries

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.

弗兰克博士和他的团队研究了低质量和中等质量恒星的恒星演化后期，当这些恒星演化成原行星状星云（PPN）和行星状星云（PN）时，它们的大部分质量都会流失到星际介质中。原行星状星云经常显示出准直的能量外流，这不能用辐射驱动来解释，原行星状星云的发射或准直还没有得到很好的理解。 该团队开发了一种新的范式，其中双星和磁流体动力学过程是大多数PPN和PN的原因。研究人员确定了PPN和PN中磁离心发射过程的潜在功效，并发现了二元伴侣为磁流体动力学发射创造条件的途径，包括发电机过程的功效。这里的工作集中在几个主题：模拟的路径吸积盘形成的PPN和PN的二元系统风捕获;共同的信封演变的背景下，PPN/PN了解磁盘形成后，喷射的散装恒星信封;和传播的磁占主导地位的磁塔喷流，这是可能导致磁盘。磁流体动力外流模拟相比，在帝国理工学院在伦敦，产生超快模式，辐射磁等离子体外流和射流的实验室天体物理实验。所有计算都使用罗切斯特大学建造的自适应网格细化磁流体动力学多物理场代码AstroBEAR。AstroBEAR代码的并行AMR引擎将被重新设计，以使其能够在大规模并行平台上实现Petascale计算。这项工作是相关的其他研究领域，其中观察到的准直流出从中央引力源。该项目提供计算天体物理学的学生和博士后培训，并促进天文学家和等离子体实验学家之间的密切联系。