Circumstellar Interaction in Type Ia Supernovae and Their Remnants: Clues to the Type Ia Phenomenon

超新星参与了当前天体物理学中许多最紧迫的问题。特别是，Ia型超新星被召唤来提供宇宙中大部分的铁，它们明亮的、几乎均匀的爆炸允许绘制宇宙的S膨胀图。尽管有这样的重要性，Ia型超新星的前驱系统仍然没有得到明确的确定，爆炸机制本身也鲜为人知。但近年来的几个趋势带来了新的进步希望。在理论方面，已经证明，在爆炸前的相当长一段时间内，涉及一颗从伴星吸积而来的单一简并恒星的前身系统会产生强烈的、快速的风。这种风对S系统周围环境和伴星本身的影响还没有得到很好的模拟。与此同时，越来越多的证据表明，至少有几个Ia型超新星确实涉及到与恒星周围物质的相互作用，而高速吸收线现在通常出现在Ia型光谱中。从几个Ia型系统中观察到了光(和红外)回波，这表明在某些情况下，尘埃距离超新星非常近。最后，超新星遗迹揭示的超新星诞生事件比人们想象的要多得多，主要是通过X射线光谱分析。喷出物的证据在相当数量的遗迹中清晰可见，这些遗迹的年龄达到或超过了10,000年。此外，一些超新星遗迹，如开普勒的S，显示出明确的证据表明，之前曾与致密的星周介质相互作用。这些诱人的线索可能不仅是几个Ia型反常超新星的本质的关键，也是整个Ia型现象的关键。在这个项目中，雷诺兹博士及其合作者将进行一系列多维流体动力学模拟，旨在连接前驱系统、超新星本身及其残骸。将研究快速的白矮风对伴星和周围物质的影响，以确定超新星前的直接环境。模型爆炸将在这些环境中引爆，以确定与星际物质相互作用的光学、红外和无线电线索，既可以解释观察到的系统，也可以在看不到发射的情况下解释上限。超新星将在数值上演化到开普勒等年轻超新星遗迹的年龄，以与它们的结构进行比较，然后跟踪到更大的年龄，以与几个麦哲伦星云遗迹进行比较，这些遗迹似乎需要强烈的星际相互作用来解释它们的X射线性质。这项工作的成果将具有广泛的适用性。Ia型超新星起源的本质问题与当今天文学中的一些最重要的问题有关，对银河系化学进化和宇宙学都有影响。这项工作将允许在超新星遗迹、产生它们的超新星和那些超新星的祖先之间建立更紧密的联系，这对所有三个研究领域都是有利的。研究生、本科生和高中生都将参与到这项工作的各个方面。雷诺兹博士和他的合作者还将利用这项研究的结果，继续向从业余天文学家到小学生的群体推广。

Supernovae are involved in many of the most pressing current questions in astrophysics. In particular, Type Ia supernovae are called on to provide much of the iron in the Universe, and their bright, almost uniform explosions allow the mapping of the Universe''s expansion. In spite of this importance, the progenitor systems of Type Ia supernovae are still not unambiguously identified, and the explosion mechanism itself is poorly understood. But several trends in recent years have brought new hope of progress. On the theoretical front, progenitor systems involving a single degenerate star accreting from a companion have been shown to produce a strong, fast wind for substantial periods of time before the explosion. The effects of this wind on the system''s surroundings, and on the companion star itself, have not yet been well modeled. At the same time, evidence has been mounting that at least a few Type Ia supernovae do involve interaction with circumstellar material, while high-velocity absorption lines are now commonly seen in Type Ia spectra. Light (and infrared) echos have been seen from a few Type Ia systems, indicating in some cases dust quite close to the supernova. Finally, supernova remnants are revealing far more about their birth events than had been thought possible, primarily through X-ray spectroscopy. Evidence of ejecta is clearly seen in significant numbers of remnants with ages up to and beyond 10,000 years. In addition, some supernova remnants, such as Kepler''s, show clear evidence for prior interaction with a dense circumstellar medium. These tantalizing clues may hold the key to the nature of not just a few anomalous Type Ia supernovae, but of the entire Type Ia phenomenon. In this project, Dr. Reynolds and collaborators will undertake a series of multi-dimensional hydrodynamic simulations designed to connect the progenitor systems, the supernovae themselves, and their remnants. The effect of a fast white-dwarf wind on the companion and on surrounding material will be studied in order to characterize the immediate pre-supernova environment. Model explosions will be set off in the midst of these environments to identify optical, infrared, and radio clues to the interaction with circumstellar material, both to explain observed systems and to interpret upper limits when emission is not seen. The supernovae will be numerically evolved to the age of young supernova remnants such as Kepler, to compare with their structure, and then followed to much larger ages, to compare with several Magellanic Cloud remnants which seemingly require strong circumstellar interaction to explain their X-ray properties. The results of this work will have broad applicability. The question of the nature of Type Ia supernova origins is connected with some of the most significant questions in astronomy today, with implications for galactic chemical evolution as well as cosmology. This work will allow a much tighter connection to be drawn between supernova remnants, the supernovae that produce them, and the progenitors of those supernovae, to the mutual benefit of all three areas of research. Graduate students, undergraduates, and high-school students will be involved in all aspects of this work. The results of this research will also be used by Dr. Reynolds and collaborators in their continued outreach efforts to groups from amateur astronomers to elementary-school children.