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中由恒星、气体和尘埃组成的圆盘状分布的螺旋臂上。地球形成于太阳形成后遗留下来的圆盘状物质中。黑洞周围有物质盘在旋转，还有很多这样的圆盘无处不在的例子。因此，了解圆盘是如何形成的，并了解其中的运作过程，对于理解天体物理学中的许多物体至关重要。******我的研究计划集中在大质量恒星，特别是b发射恒星（Be星），被圆盘包围。各种各样的技术被用来观察这些非常明亮的物体，为研究磁盘提供了理想的环境。这些恒星每秒释放的能量是太阳的1000倍，而在我们的银河系中就有数千颗恒星。由于这个圆盘是由恒星发射的气体形成的，所以它不像恒星形成区域的圆盘那样被尘埃所笼罩，这使得be星盘更容易观察，化学组成也更简单。恒星的快速旋转导致恒星内部的物质被搅动，最终影响能量的产生及其寿命。当一颗Be星到达其生命的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。******尽管经过了几十年的研究，在这个研究领域中，最基本的问题是为什么会形成圆盘。恒星的快速旋转肯定有助于将物质从表面推入圆盘，但必须有别的东西帮助将物质抛射出去，可能是轨道恒星的引力，恒星表面的波或脉动，或者恒星辐射的推力。******当来自Be星的光穿过圆盘时，它被散射、吸收和重新发射，这导致了发射光的变化。我建立了详细的计算机模型来预测在大波长范围内（颜色）发射的光的特征。圆盘内的温度分布非常复杂，这导致圆盘不同区域产生不同的波长。这个想法是，如果我们得到恒星参数和磁盘条件，如化学成分，温度和密度正确，我们将能够在这个宽范围内匹配光中的特征。然后，我们可以构建可靠地跟踪磁盘结构的模型，以更好地理解磁盘的工作原理。******在加拿大，特别是在西部大学，对Be星盘的特定学科研究和专业知识有着悠久的历史。我的项目的结果不仅将为理解这种类型的磁盘提供关键结果，而且将帮助全世界的研究人员应用这一见解来更好地理解其他磁盘品种，对大质量恒星的形成以及恒星和星系的演化施加限制。*****

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.*****