Circumstellar Disks Surrounding Massive Stars

在可观测的宇宙中，可以发现许多不同类型的气体、恒星和行星的盘状分布。我们的太阳位于银河系恒星、气体和尘埃的盘状分布中的螺旋臂上。地球是由太阳形成时遗留下来的物质组成的圆盘。黑洞有由物质组成的圆盘围绕着它们旋转，而且还有更多的例子表明这种圆盘无处不在。因此，了解圆盘是如何形成的并欣赏在其中运行的过程对于理解天体物理学中的许多物体是至关重要的。 我的研究项目专注于大质量恒星，特别是被圆盘包围的B发射恒星(Be恒星)。各种技术被用来观察这些非常明亮的物体，这为研究磁盘提供了一个理想的环境。Be星每秒释放的能量是太阳的1000倍，而数千颗Be星就生活在我们的银河系中。由于Be星盘是由恒星发出的气体形成的，所以它往往不会像恒星形成区那样被尘埃笼罩着，这使得Be星盘更容易观察，化学组成也更简单。恒星的快速自转导致恒星内部的物质被搅动，最终影响到能量的产生和寿命。当一颗Be星到达寿命尽头并成为超新星时，它可以触发新一代恒星的出现，直接影响其母星系的演化。 尽管进行了几十年的研究，但这一研究领域需要解决的根本问题是为什么会形成圆盘。恒星的快速自转当然有助于将物质从表面推入圆盘，但一定有其他东西帮助弹出物质--可能是来自轨道恒星的重力、恒星表面的波动或脉动，或者是恒星辐射的推动。 当Be恒星发出的光穿过圆盘时，它被散射、吸收并重新发射，这会导致发射的光发生变化。我建立了详细的计算机模型，预测在大范围的波长(颜色)范围内发射的光的特征。盘中的温度分布非常复杂，这导致盘的不同区域产生不同的波长。我们的想法是，如果我们得到正确的恒星参数和盘状条件，如化学成分、温度和密度，我们将能够在这个大范围内匹配光的特征。然后，我们可以构建可靠地跟踪磁盘结构的模型，以便更好地了解磁盘的工作原理。 在加拿大，特别是在西方大学，对Be星盘的特定学科的研究和专业知识有很长的历史。我的计划的结果不仅将为理解这种类型的盘提供关键结果，而且将帮助世界各地的研究人员应用这一洞察力来更好地了解其他盘类型，从而限制大质量恒星的形成和恒星和星系的演化。

Many different types of disk-like distributions of gas, stars, and planets can be found in the observable universe. Our own Sun is located in a spiral arm within a disk-like distribution of stars, gas and dust in our Milky Way Galaxy. The Earth formed in a disk of material left over from the formation of the Sun. Black holes have disks of material swirling about them, and there are many more examples of the ubiquity of such disks. Consequently, knowing how disks form and appreciating the processes operating in them are critical to understanding many objects in astrophysics. My research program focuses on massive stars, in particular B-emission stars (Be stars), that are surrounded by disks. A variety of technologies are employed to observe these remarkably bright objects which provide an ideal environment for studying disks. Be stars can spew out one thousand times more energy per second than our Sun and thousands exist right in our own Galaxy. Since the disk is formed from gas launched from the star, it tends not to be shrouded in dust like disks in star forming regions which makes Be star disks easier to observe and the chemical makeup simpler. The star's fast rotation causes materials inside the star to be stirred up, ultimately affecting the production of energy and its lifetime. When a Be star reaches the end of its life and goes supernova, it can trigger the emergence of a new generation of stars, directly affecting the evolution of its parent galaxy. Despite decades of study, the fundamental question to be solved in this field of study is why the disk forms. The rapid rotation of the star certainly helps to propel material off the surface into the disk, but something else must help to eject the material - perhaps gravity from an orbiting star, a wave or pulsation on the stellar surface or a push from the stellar radiation. When the light from the Be star goes through the disk, it is scattered, absorbed and re-emitted and this causes changes in the light emitted. I build detailed computer models that predict signatures in the emitted light over a large range of wavelength (colour). The temperature distribution in the disk is highly complex which causes different areas of the disk to produce different wavelengths. The idea is that if we get stellar parameters and disk conditions such as the chemical composition, temperature and density correct, we will be able to match the signatures in the light over this wide range. Then we can build models that reliably follow the disk structures over time to better understand how disks work. There is a long history of discipline-specific study and expertise in Canada, in particular at Western University, of Be star disks. The results of my program will not only provide key results for understanding this type of disk but will help researchers worldwide apply the insight to better understand other disk varieties, placing constraints on the formation of massive stars and on the evolution of stars and galaxies.