Studies in Common Envelope Evolution

最近Chandra和XMM牛顿对银河系和外部星系中的点X射线源群的观测，重新引起了人们对具有致密组件的紧密相互作用的双星系统演化的兴趣。观测到的这些系统的质量和轨道周期很难理解，需要大量的质量和角动量损失。一个促进这些损失的演化通道涉及到角动量和能量从双星轨道转移到一个公共包络，然后这个公共包络被抛出。这个项目将研究双星演化的所谓公共包络阶段。将特别关注含有白矮星的激变双星系统的形成，以及含有中子星和黑洞成分的中低质量X射线双星。这项研究的主要目的是描述参数空间中的区域，这些区域将双星从长轨道周期的双星转换到短轨道周期的双星，作为后公共包络幸存者从合并成单个快速旋转的物体的系统中分离出来。这些研究涉及多维流体动力学过程的处理，需要高分辨率的三维数值模拟。为了进行这些模拟，将使用经过特别修改以处理公共包络问题的自适应并行模拟代码。这项研究最终将提供一个基础，在此基础上可以理解包含致密天体的紧密双星系统的形成和演化。这些项目的影响预计将在当代天体物理学的广泛领域中感受到，包括X射线天文学、引力理论、超新星理论和激变变星研究。此外，它还将有助于科学人力资源的培训和教育，因为有效利用高性能并行计算体系结构所涉及的数值技术和方法以及解决这些问题所需的数据管理技能在这里所侧重的具体领域之外还有许多应用。结果将在芝加哥的阿德勒天文馆和天文博物馆向公众展示。其目标将是向公众展示可视化在科学发现和研究中的重要性，以及传达这种工具可以是学习科学思想的有效手段。研究结果还将被纳入西北大学物理与天文学系开设的入门和高级课程。

Recent Chandra and XMM Newton observations of the point X-ray source population in the Milky Way and external galaxies have led to a resurgence of interest in the evolution of close interacting binary systems with compact components. The observed masses and orbital periods for these systems are difficult to understand and require significant loss of both mass and angular momentum. An evolutionary channel which facilitates these losses involves the transfer of angular momentum and energy from the binary orbit to a common envelope which is subsequently ejected.This so-called common envelope phase of binary evolution will be investigated in this project. Particular attention will be focused on the formation of cataclysmic variable binary systems containing white dwarf compact stars as well as on intermediate and low mass X-ray binaries containing neutron star and black hole components. The primary goal of this research is to delineate the regions in parameter space separating progenitor systems in which the binary is transformed from one at long orbital periods to one at short orbital periods as a post common envelope survivor from systems which merge into a single rapidly rotating object.These studies will involve the treatment of multi-dimensional hydrodynamical processes and require high resolution three dimensional numerical simulations. To carry out these simulations, an adaptive, parallel simulation code that has been especially modified to treat the common envelope problem will be employed. The research will ultimately provide a foundation upon which the formation and evolution of close binary systems containing compact objects can be understood.The impact of these projects is expected to be felt across a broad spectrum of contemporary astrophysics including X-ray astronomy, gravitational theory, supernova theory, and cataclysmic variable star research. In addition, it will aid in the training and education of human resources in science since the numerical techniques and methodologies involved in the efficient use of high performance parallel computing architectures and the data management skills required for the solution of these problems have many applications outside of the specific areas focused upon here. The results will be visualized for the general public at the Adler Planetarium & Astronomy Museum in Chicago. The goal will be to show to the public the importance of visualization in scientific discovery for research as well to convey that such tools can be effective means for learning scientific ideas. The results will also be incorporated into both introductory and advanced courses offered by the Department of Physics and Astronomy at Northwestern University.