The Role of Circumstellar Disks in Massive Star Formation and Evolution

星周盘在大质量恒星形成和演化中的作用

• 批准号: RGPIN-2018-05978
• 负责人: Sigut, Thomas
• 金额: $ 1.75万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=680037
• 关键词: Role; Circumstellar; Disks; Massive; Star

Stars with masses greater than eight times the mass of our Sun play a critical role in the Milky Way Galaxy. Their high luminosities and winds are important sources of energy and matter input into the interstellar gas and dust between the stars. Supernova explosions, which occur at the end of the lives of these massive stars, inject even larger amounts of energy and matter into the interstellar medium, including newly synthesized heavy elements or "metals." This material is incorporated into new generations of stars and planetary systems, which become more metal rich over time. The remnants left behind after supernova explosions, neutron stars and black holes, give rise to some of the most exotic phenomena in the Universe, such as gamma-ray bursts and gravitational waves. Understanding the life cycles of these massive stars underlies much of our current understanding of the Universe, from the evolution of galaxies, to the formation of the first generation of stars. Many massive stars rotate very rapidly, in just a day or two, and the theoretical treatment of rapid rotation has been identified as a key uncertainty in our understanding of how these stars evolve and die. Rapid rotation can mix material and angular momentum within a star and, in some cases, it can lead to the ejection of gas from the star's atmosphere into a circumstellar disk. The current treatment of both of these processes is highly uncertain, and new observational constraints will play an important role is making the predictions of stellar evolution with rotation more accurate. The research proposed in this Discovery Grant will focus on rapidly rotating, massive stars that have ejected circumstellar disks, using them as "astrophysical laboratories" in which to better understand how rotation affects their lives. Spectroscopic observations will be analyzed for the signature of elements produced in stellar cores by fusion and transported to the surface by rotational mixing. Interferometric observations will be used to determine the masses of the circumstellar disks ejected by these stars. Spectroscopic analysis will be extended to massive stars in the Large and Small Magellanic Clouds, satellite galaxies of our Milky Way with stars that are metal poor. As larger ground-based and space-based telescopes extend observations to ever more distant, early, and metal-poor epochs in the Universe, it is critical to improve our understanding of stellar evolution in rapidly-rotating, metal-poor stellar systems in order to properly take advantage of the flood of new observational data. Students are an integral part of the proposed research program, and they will receive training in radiative transfer, high performance computation, data modelling, and scientific communication. These students will also have access to inter-disciplinary training through Western's collaborative graduate programs in Planetary Science and Scientific Computing.

质量大于太阳八倍的恒星在银河系中起着至关重要的作用。它们的高亮度和风是输入星际气体和恒星之间尘埃的重要能量和物质来源。发生在这些大质量恒星寿命结束时的超新星爆炸，向星际介质注入了更大数量的能量和物质，包括新合成的重元素或“金属”。这种材料被并入新一代恒星和行星系统，随着时间的推移，它们变得更加富含金属。超新星爆炸、中子星和黑洞留下的残留物，引发了宇宙中一些最奇异的现象，如伽马射线爆发和引力波。从星系的演化到第一代恒星的形成，了解这些大质量恒星的生命周期，在很大程度上奠定了我们目前对宇宙的理解。许多大质量恒星的自转速度非常快，只需一两天，而快速自转的理论处理已被认为是我们理解这些恒星如何进化和死亡的关键不确定性。快速自转可以混合恒星内部的物质和角动量，在某些情况下，它可以导致气体从恒星的大气层喷射到恒星周围的圆盘中。目前对这两个过程的处理都高度不确定，新的观测约束将发挥重要作用，使恒星旋转演化的预测更加准确。在这项发现拨款中提出的研究将专注于快速旋转的大质量恒星，这些恒星抛出了恒星周围的圆盘，将它们用作“天体物理实验室”，在其中更好地了解旋转如何影响它们的生活。将对光谱观测进行分析，以确定恒星核心通过聚变产生的元素的特征，并通过旋转混合将元素输送到表面。干涉观测将被用来确定由这些恒星抛出的星周圆盘的质量。光谱分析将扩展到大小麦哲伦星云中的大质量恒星，这些大小麦哲伦星云是我们银河系的卫星星系，其恒星缺乏金属。随着更大的地面和天基望远镜将观测扩展到宇宙中更遥远、更早、更缺乏金属的时期，为了适当地利用大量新的观测数据，提高我们对快速旋转、缺乏金属的恒星系统中恒星演化的理解是至关重要的。学生是拟议研究计划的组成部分，他们将接受辐射传输、高性能计算、数据建模和科学交流方面的培训。这些学生还将有机会通过WESTERN在行星科学和科学计算方面的合作研究生项目进行跨学科培训。