Rotational Evolution of Massive Stars

大质量恒星的旋转演化

• 批准号: 0606861
• 负责人: Douglas Gies
• 金额: $ 28.03万
• 依托单位: Georgia State University Research Foundation, Inc.
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0606861&HistoricalAwards=false
• 关键词: Rotational; Evolution; Massive; Stars

This project is motivated by the need to better understand the evolution of massive starsas shapers of the interstellar medium through ionization and winds, sources of heavyelements throughout Galactic history, and as the progenitors of supernovae. In particular,the rotation properties of massive early-type OB stars play a key role in their evolution asrapid rotation can trigger strong mixing which can in turn extend their core-hydrogenburning lifetimes, significantly increase their luminosities, and change the chemicalcompositions of their surfaces. Indeed, some massive stars may even experience a shortepisode of faster rotation during their approach to the terminal main sequence (caused bychanges in internal structure) which may account for the occurrence of the rapidlyrotating Be stars, B-type stars with Balmer line emission and an infrared excess due to acircumstellar disk.Observational studies of stellar rotation are problematic because in most cases it is difficult to determine the inclination of the spin axis relative to our line of sight. However, this shortcoming can be overcome in statistical analyses of large samples of targets. The purpose of this investigation is to obtain such data on the projected rotational velocities of a significant sample of massive B-type stars in young open clusters. Model line synthesis codes will be used to determine fundamental stellar parameters such as effective temperature and gravity in order to show how the rotational properties vary from the pre-main sequence phase, through the duration of the main sequence lifetime, and up to the terminal age main sequence. The spectra will also be analyzed to determine the influence of rotation on mixing of CNO processed gas into the surface layers. The results will provide the crucial means to test modern evolutionary codes and to aid in our interpretation of the properties of young stellar clusters and associations.A second aspect of the program is a study of the physical processes in stars that arespinning so fast that the centrifugal and gravitational accelerations nearly balance eachother at the stellar equator. This work will center on new observations with the GeorgiaState University Center for High Angular Resolution Astronomy Array (CHARA) atMount Wilson Observatory. This six-element, optical long baseline interferometer willresolve the shapes and sizes of these ultrafast rotators, and numerical models will beconstructed to match both the interferometric fringe data and complementary high signalto-noise spectroscopy. The goal is to determine how fast a star must rotate in order toeject matter out into a circumstellar disk of the kind found in Be stars. CHARA Arrayobservations of Be disks will help determine their size, orientation, and mass outflowrate.Through this award, a postdoctoral research fellow will be supported and trained. Thepostdoctoral fellow will also participate in instrument support and development at theCHARA Array, developing expertise in electro-optics and computation and supportingthe optical interferometer. Graduate students are also expected to be involved andeducated through the work. The results of this work will be included in introductoryastronomy course lectures and GSU and disseminated to the public through press releasesand public talks.

该项目的激励是由于有必要通过电离和风，整个银河历史上的巨大元素以及作为超新星的祖细胞来更好地了解星际介质的巨大恒星变形。特别是，大量早期型OB恒星的旋转特性在其进化中起着关键作用，可以触发强烈的混合，进而可以延长其核心 - 氢气的寿命，大大增加其亮度，并改变其表面的化学物质。实际上，某些巨大的恒星甚至可能在其进入末端主序列的方法（在内部结构中引起的字节）的速度更快旋转，这可能是迅速脱位的是恒星，B型恒星带有Balmer线发射的恒星，而Balmer线排放和相对的均具有过量的均为稳定性的均应降低，因为该病例的均具有较难的确定性，因为旋转的旋转均具有问题，因为最大的旋转均具有最大的旋转。对我们的视线。但是，在大量目标样本的统计分析中，可以克服这种缺点。这项研究的目的是获取有关年轻开放式簇中大量B型星样本的预计旋转速度的此类数据。模型线综合代码将用于确定基本恒星参数，例如有效温度和重力，以显示旋转特性如何从前序列阶段，直到主序列寿命的持续时间以及末端年龄主序列变化。还将分析光谱，以确定旋转对CNO加工气体混合到表面层的影响。结果将为测试现代进化代码的关键手段，并帮助我们解释年轻恒星簇和关联的性质。该程序的第二个方面是对恒星中的物理过程的研究，以至于阿雷斯皮（Arespin）快速地进行了速度如此之快，以至于在斯特洛尔赤道上几乎平衡了恒星和重力加速。这项工作将与乔治亚斯大学高角度分辨率天文学阵列（Chara）Atmount Wilson天文台的新观察有关。这个六元素的光学长基线干涉仪将溶解这些超快速旋转器的形状和尺寸，数值模型将构建以匹配干涉率数据和互补的高信号噪声光谱。目的是确定恒星必须旋转的速度，以使脚趾的物质旋转到恒星中发现的那种磁盘中。 Chara Arrayobsertations的BE Disks将有助于确定其规模，定向和大规模溢出。通过此奖项，将支持和培训博士后研究员。 postdoctoral研究员还将在Thechara阵列中参与仪器支持和开发，开发电脑和计算方面的专业知识，并支持光学干涉仪。预计研究生还将在工作中得到教育。这项工作的结果将包括在入门课程课程讲座和GSU中，并通过新闻稿和公众演讲向公众传播。