The physical nature of be stars and their circumstellar disks

旋转，或“自旋”，在宇宙中无处不在。地球、太阳和银河系都在自转。所有这些物体都是由大爆炸后的引力坍缩形成的，这种坍缩自然地增加了任何初始的小的随机旋转。一个有趣的问题是，这种旋转如何塑造恒星、行星和星系的生命。天文学家知道，快速旋转可能是质量超过太阳三倍的恒星演化的关键因素。虽然这样的恒星比太阳质量的恒星更稀有，但它们为银河系的星际介质提供了大部分的能量和质量（新恒星形成），并且它们合成了（通过核燃烧和超新星爆炸）所有生命所必需的化学元素。然而，对自转在大质量恒星生命中所起作用的连贯理解还远未完成。我的研究将通过关注旋转最快的核心氢燃烧恒星，即B发射线或Be恒星来解决这个问题。Be恒星的自转周期约为一天（太阳的自转周期约为一个月），并且已知它们的赤道周围有一个气体盘。然而，Be星的自转速率是高度不确定的，快速自转在形成其盘中所扮演的角色也是未知的。我将使用新的计算技术，沿着新的观测结果，其中一些是在加拿大-法国-夏威夷望远镜上获得的，以准确地估计Be星旋转的速度。任何关于它们的圆盘如何形成的模型都必须与这些旋转速率相一致。我还将尝试探测这些恒星大气中元素丰度的模式，以找到Be恒星内部混合的第一个证据，这些内部混合是由快速旋转驱动的。这将对大质量恒星的旋转演化产生重要的新约束，并可能有助于理解宇宙中的奇异事件，例如伽马射线爆发，它是由质量最大的快速旋转恒星的超新星爆炸形成的。加拿大作为一个整体将受益于这项研究，通过研究生在高性能计算和数据可视化完成这些研究项目所需的培训。

Rotation, or "spin," is ubiquitous in the Universe. The Earth, the Sun, and the Milky Way Galaxy all rotate. All of these objects formed from gravitational collapse after the Big Bang, and this collapse acts naturally to increase any initial small, random rotation. An intriguing question is how this rotation shapes the lives of stars, planets, and galaxies. Astronomers know that rapid rotation can be a key element in the evolution of stars more massive than about three times the mass of the Sun. While such stars are rarer than solar-mass stars, they supply most of energy and mass to the interstellar medium of the Milky Way (out of which new stars form), and they synthesize (through nuclear burning and supernova explosions) all of the chemical elements essential for life. However a coherent understanding of the role rotation plays in the lives of massive stars is far from complete. My research will address this problem by focusing on the most rapidly rotating, core hydrogen burning stars, the B emission-line or Be stars. Be stars rotate with periods of about one day (compared to about one month for our Sun), and they are known to possess a disk of gas surrounding their equator. However, rotation rates for Be stars are highly uncertain, and the role that rapid rotation plays in forming their disks is unknown. I will use new computational techniques, along with new observations, some obtained at the Canada-France-Hawaii Telescope, to accurately estimate how fast Be stars rotate. Any model of how their disks form will have to be consistent with these rotation rates. I will also attempt to detect patterns in the abundances of the elements in the atmospheres of these stars to find the first evidence for internal mixing in Be stars driven by their rapid rotation. This will place important new constraints on the rotational evolution of massive stars and will potentially help to understand exotic events in the universe, such as gamma-ray bursts which are though to form from the supernova explosions of the most massive, rapidly rotating stars. Canada as a whole will benefit from this research through the graduate students trained in high-performance computation and data visualization required to complete these research projects.