The Dynamics and Energetics of Circumbinary Discs

这个学生项目将需要调查银河系中质量比和偏心率不同的双星系统的环绕双星轨道。这些研究将通过计算和直接成像来自全球喷气观测站的光谱数据的时间序列进行。这是一个富有成果和重要的研究领域，原因如下：-行星：2011年9月(我和我的上一个博士生和我发表了一篇关于3D N体模拟的论文三周后)发现了第一颗绕双星(开普勒16b)，论文毫无疑问地证明，如果稳定的定义足够自由，包括在这些轨道平面中的进动，那么稳定的外双星轨道是存在的。我们发现了三个非常稳定的轨道家族，在那项工作中描述了，在过去的几年里，开普勒和其他任务发现了更多的周转双星。气体如何在与行星形成相适应的时间尺度上冷却和凝聚--偏心率--仍有待探索和理解：为什么一些双星系统的偏心率在它们本应环行很长时间后仍然存在，这仍然是一个谜。有人提出，外双星轨道上的天体不仅可以保持这种偏心率，而且还可以驱动这种偏心率，但当第三个天体被涂抹成环或盘时，以及当这个实体进动时，如何发生这种情况仍有待探索。-质量损失：在迄今唯一被充分研究的外双星盘中，银河系微类星体SS433的外双星盘的质量损失量与其吸积盘风造成的质量损失量非常相似。为了正确地解释这种双星系统中质量传递和质量损失是如何发生的，以及更广泛地说双星演化是如何进行的，有必要了解从绕双星轨道上的物质失去的质量所起的作用-吸积：Krolik(Johns Hopkins)已经提出，外转双星盘实际上可以是双星通过它从周围吸收物质的方式。考虑到这四个区域的重要性，这表明现在是集中研究它们的好时机：通过计算模型和直接的长期时间序列光谱，这是我在过去一年多的时间里从我的Global Jet Watch天文台为这名学生收集的。

The student project will entail investigations of circumbinary orbits around binary star systems in the Galaxy of varying mass ratio and eccentricity. These investigations will take place via computational calculation and via direct imaging of time series of spectroscopic data from the Global Jet Watch observatories. This is a fruitful and important area of study for the following four reasons:- PLANETS: The first circumbinary planet (Kepler 16b) was discovered in September 2011 (three weeks after my previous Doctoral student and I published a paper on 3D N-body simulations that had demonstrated beyond doubt the existence of stable circumbinary orbits if the definition of stable is sufficiently liberated as to include precession in these orbital planes. We discovered three remarkably stable families of orbits, described in that work, and in the last few years Kepler and other missions have discovered further circumbinary planets. It remains to be explored and understood how the gas can cool and coalesce on a timescale appropriate to planet formation- ECCENTRICITY: It remains a mystery why the eccentricity of some binary star systems persists long after they should have circularised. It has been suggested that a body in a circumbinary orbit can not only preserve but drive this eccentricity, but it remains to be explored how this can take place when that third body is smeared out into a ring or disc, and furthermore, when this entity is precessing. - MASS-LOSS: in the only circumbinary disc well-studied to date, that of the Galactic microquasar SS433, the amount of mass-loss from the circumbinary disc is very comparable with that lost via its accretion disc wind. In order to properly account for how mass-transfer and mass-loss takes place in such binary systems, and more broadly how binary evolution proceeds, it is essential to understand what part is played by mass lost from the matter on circumbinary orbits- ACCRETION: Krolik (Johns Hopkins) has suggested that circumbinary discs can actually be the means by which binaries can accrete material from their surroundings. Given the importance of these four areas separately, this suggests that this is an opportune time to investigate them collectively: via computational modelling and via direct long-term times series spectroscopy that I have been collecting for this student over the last 1+ year from my Global Jet Watch observatories.