Origin of massive high-velocity stars in the halo

晕中大质量高速恒星的起源

• 批准号: 386788844
• 负责人: Professor Dr. Ulrich Heber
• 金额: --
• 依托单位: Astronomisches Rechen-Institut
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/386788844?language=en
• 关键词: Origin; massive; velocity; stars; halo

Twelve years after their serendipitous discovery in 2005, hyper-velocity stars (HVSs) are more than ever a hot topic and interest will be boosted in the Gaia era which started right now. These objects are late B-type stars that move with very high velocities through our Galaxy, and most of them are even gravitationally unbound to our Milky Way. Initially, the dynamical interaction with the supermassive black hole in the Galactic centre (GC) was their only suggested origin. In the meantime, however, more and more massive high-velocity stars were found that did not originate in the GC and thus challenged this picture. Those stars are extreme cases of so-called runaway stars, a well-known group of kinematically peculiar stars which can be ejected from their environment by dynamical interactions in star clusters or by a supernova explosion disrupting a binary system. An extragalactic origin from the Large Magellanic Cloud or disrupted dwarf satellite galaxies is also considered possible. Our work during the past couple of years has revealed strong links between runaway stars and HVSs. Consequently, trying to understand the one class of stars requires to understand the other class as well. Therefore, we had extended our research projects to a broad range of high-velocity stars. The goal of this project is to understand the origin and nature of massive runaway and HVSs. This requires a combination of quantitative spectroscopic and astrometric/kinematic analyses. Improved model atmospheres and novel spectral diagnostic tools derived in our team shall be applied to high fidelity optical spectra, partly already at hand. Gaia astrometry will be the backbone of the project. These data can be utilized, for example, to improve Galactic mass models and to trace back stellar trajectories to their places of origin. Furthermore a complete sample of high-velocity stars can be established to test population synthesis models. The places of origin as well as the ejection mechanisms will be identified from chemical tagging combined with the information from Gaia astrometry.

在2005年偶然发现的12年后，超高速恒星（HVS）比以往任何时候都更是一个热门话题，人们对现在开始的盖亚时代的兴趣将得到提升。这些物体是晚期的B型恒星，它们以非常高的速度穿过我们的银河系，其中大多数甚至与我们的银河系没有引力。最初，与银河系中心（GC）超大质量黑洞的动力学相互作用是它们唯一的起源。然而，与此同时，越来越多的大质量高速恒星被发现，它们不是起源于GC，从而挑战了这一观点。这些恒星是所谓的失控恒星的极端例子，失控恒星是一组众所周知的运动学上奇特的恒星，它们可以通过星星团中的动力学相互作用或超新星爆炸破坏双星系统而从环境中弹射出来。来自大麦哲伦星云或破裂的矮卫星星系的河外起源也被认为是可能的。我们在过去几年的工作揭示了逃逸恒星和HVS之间的密切联系。因此，要想理解一类恒星，就必须同时理解另一类恒星。因此，我们将研究项目扩展到了广泛的高速恒星。这个项目的目标是了解大规模失控和HVSs的起源和性质。这需要结合定量光谱和天体测量/运动学分析。改进的模型大气和新的光谱诊断工具，在我们的团队中得出的高保真光谱，部分已经在手。盖亚天体测量将是该项目的支柱。例如，这些数据可以用来改进银河系质量模型，并追溯恒星轨迹到它们的起源地。此外，可以建立一个完整的高速星样本来测试人口合成模型。起源地以及喷射机制将通过化学标记结合盖亚天体测量的信息来确定。