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

超新星涉及到当前天体物理学中许多最紧迫的问题。特别是，Ia型超新星被认为提供了宇宙中大部分的铁，它们明亮、几乎均匀的爆炸使得绘制宇宙膨胀的地图成为可能。尽管具有这种重要性，但Ia型超新星的祖系统仍然没有得到明确的识别，而且爆炸机制本身也知之甚少。但近年来的一些趋势带来了取得进展的新希望。在理论的前沿，包含单个简并恒星从伴星中吸积的祖星系已经被证明在爆炸前的相当长一段时间内会产生强劲、快速的风。这种风对系统周围环境的影响，以及对伴星本身的影响，尚未得到很好的模拟。与此同时，越来越多的证据表明，至少有一些Ia型超新星确实与星周物质相互作用，而高速吸收谱线现在在Ia型光谱中很常见。从一些Ia型系统中可以看到光（和红外）回波，这表明在某些情况下，尘埃离超新星很近。最后，主要通过x射线光谱学，超新星遗迹揭示的关于其诞生事件的信息远远超出了人们的想象。在大量的遗迹中可以清楚地看到喷出物的证据，这些遗迹的年龄可达或超过1万年。此外，一些超新星遗迹，如开普勒的遗迹，显示出与密集的星周介质相互作用的明确证据。这些诱人的线索可能不仅掌握了一些异常Ia型超新星的本质，而且掌握了整个Ia型现象的本质。在这个项目中，雷诺兹博士和合作者将进行一系列多维流体动力学模拟，旨在连接祖系统、超新星本身和它们的残余物。快速白矮星风对伴星和周围物质的影响将被研究，以表征超新星爆发前的直接环境。模型爆炸将在这些环境中引爆，以识别与星周物质相互作用的光学、红外和无线电线索，既可以解释观测到的系统，也可以解释未观测到发射时的上限。这颗超新星将在数值上演化到像开普勒这样的年轻超新星遗迹的年龄，与它们的结构进行比较，然后再与更大的年龄进行比较，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周相互作用来解释它们的x射线特性。这项工作的结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一些最重要的问题有关，对星系化学演化和宇宙学都有影响。这项工作将使我们在超新星遗迹、产生它们的超新星和这些超新星的祖先之间建立更紧密的联系，从而使这三个研究领域都受益。研究生、本科生和高中生将参与这项工作的各个方面。这项研究的结果也将被雷诺兹博士及其合作者用于他们继续向从业余天文学家到小学生的团体推广的努力。

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.