From Core to Outflow: Binaries, MHD and the Origin of Planetary/ Pre-Planetary Nebulae

这个项目是弗兰克博士和布莱克曼博士为更好地理解行星状星云的形成过程以及低质量和中等质量恒星演化的后期阶段所做努力的延续。作为这类恒星质量损失的最后阶段，行星状星云代表了一半以上的物质喷射到星际介质中的质量和化学演化周期的关键步骤。行星状星云无处不在，而且易于观测，这也使它们成为检验新的天体物理理论的首选实验室。最近，行星状星云及其前身（前行星状星云）的高分辨率图像引发了对星云形成和恒星演化的主要模型的关键重新评估。对行星前星云的研究表明，它们是准直的，并驱动能量外流，而这些外流缺乏足够的亮度来进行辐射驱动。因此，前行星状星云的发射或准直，以及与之相关的行星状星云，不能被认为是可以理解的。根据新的数据，关于行星前和行星状星云演化的理论，以及由此产生的关于恒星演化后期过程的观点正在经历根本性的修正。一种新的图景正在出现，其中双星和磁流体动力学（MHD）过程是大多数前行星和行星状星云的原因。博士之前的工作。弗兰克和布莱克曼已经确定了磁离心式发射过程在这些系统中的潜在功效。他们展示了双星伴星可以为MHD的发射创造条件的途径，包括双星中发电机过程的有效性及其在单星中的局限性。该项目将以这一进展为基础，有三个具体目标：1)对双星发电机提供的磁场条件提供更准确的描述；2)探索圆盘的形成，这些圆盘产生的流出物，以及产生的形态和观测特征；3)了解由双星发电机驱动的磁塔爆炸的产生。目标2和3将使用Frank博士和合作者开发的新的自适应网格细化MHD代码（AstroBEAR）来实现。此外，该项目将为伦敦帝国理工学院的一系列实验室天体物理学实验提供持续的理论支持，这些实验对天体物理学具有广泛的兴趣，并与行星前星云和行星状星云直接相关。在天体物理学中，中心引力源的准直流出是一种普遍存在的现象。在新形成的恒星、高度演化的大质量恒星、双星中的致密天体、星暴星系和为活动星系核提供动力的超大质量黑洞中，可以观察到喷流和更宽的双极流出。准直喷流也被用于超新星和伽马射线爆发的模型中。虽然这项工作的重点是行星状星云，但它将在理论上和观测上与这些其他领域直接相关，因为它允许行星状星云作为MHD流出理论的试验台。与帝国大学团队的合作将有助于深化高能量密度实验室天体物理学这一快速发展的领域。开发AstroBEAR代码的工作对继续使用新的多物理方法进行研究以及培训下一代计算天体物理学家特别有益。最后，该计划还包括一个创新的推广计划，包括创建科学互动：基于模拟的学习模块，这些模块将发布在全国最受欢迎的科学杂志网站上。

This project is a continuation of Dr. Frank and Dr. Blackman's efforts better to understand the process of planetary nebula formation and the late stages of evolution of low and intermediate mass stars. As the final stage of mass loss for such stars, planetary nebulae represent a critical step in the mass and chemical evolution cycle for more than half the material ejected into the interstellar medium. The ubiquity of planetary nebulae and their ease of observation have also made them premier laboratories for testing new astrophysical theories. Recently, high-resolution images of planetary nebulae and their progenitors (pre-planetary nebulae) have triggered a critical re-evaluation of the dominant model for both nebular shaping and stellar evolution. Studies of pre-planetary nebulae show them to be collimated and to drive energetic outflows that lack sufficient luminosity for radiative driving. The launching or collimation of pre-planetary nebulae, and by association planetary nebulae, therefore cannot be considered to be understood. In light of new data the theory of pre-planetary and planetary nebulae evolution and, by implication, ideas about processes at work in the late stages of stellar evolution are undergoing fundamental revision. A new picture is emerging in which binaries and magnetohydrodynamic (MHD) processes are responsible for the majority of pre-planetary and planetary nebulae. Previous work by Drs. Frank and Blackman has established the potential efficacy of magneto-centrifugal launching processes in these systems. They have shown the pathways by which binary companions can create conditions for MHD launching, including the efficacy of dynamo processes in binary stars and its limits in single stars.This project will build on this progress with three specific goals: 1) to provide a more accurate account of the field conditions supplied by dynamos in binaries, 2) to explore the formation of disks, the outflows generated by such disks, and the morphology and observational signatures produced, and 3) to understand the generation of magnetic tower explosions by binary driven dynamos. Goals 2 and 3 will be achieved using a new adaptive mesh refinement MHD code (AstroBEAR) developed by Dr. Frank and collaborators. Additionally, the project will provide continued theoretical support for a series of laboratory astrophysics experiments at Imperial College in London, which are of broad interest to astrophysics and directly relevant to pre-planetary and planetary nebulae. Collimated outflows from a central gravitating source are a ubiquitous phenomenon in astrophysics. Jets and wider bipolar outflows are observed in newly forming stars, highly evolved high mass stars, compact objects in binaries, starburst galaxies, and supermassive black holes powering active galactic nuclei. Collimated outflows are also invoked in models for supernovae and gamma ray bursts. While this work is focused on planetary nebulae it will be of direct relevance to these other fields both theoretically and observationally in the sense of allowing planetary nebula to act as a test-bed for theories of MHD outflows. The collaboration with the Imperial Collage group will help to deepen the rapidly growing field of High Energy Density Laboratory Astrophysics. The work developing the AstroBEAR code is of particular benefit in continuing research with new multi-physics methods as well as training the next generation of computational astrophysicists. Finally this program also includes an innovative outreach program involving the creation of Sci-Interactives: simulation based learning modules which will be posted on the nation's most popular science magazine websites.