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.

自 2005 年偶然发现超高速恒星 (HVS) 十二年后，超高速恒星 (HVS) 比以往任何时候都成为热门话题，并且在现在开始的盖亚时代，人们的兴趣将会更加浓厚。这些天体是晚期 B 型恒星，它们以非常高的速度穿过我们的银河系，其中大多数甚至不受银河系引力的束缚。最初，与银河中心（GC）超大质量黑洞的动力学相互作用是他们唯一提出的起源。然而，与此同时，越来越多的大质量高速恒星被发现，它们并非起源于GC，从而对这一图景提出了挑战。这些恒星是所谓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特殊的恒星，它们可以通过星团中的动态相互作用或破坏双星系统的超新星爆炸而从其环境中弹出。河外起源于大麦哲伦星云或破碎的矮卫星星系也被认为是可能的。我们过去几年的工作揭示了失控恒星和 HVS 之间的密切联系。因此，试图了解一类恒星也需要了解另一类恒星。因此，我们将我们的研究项目扩展到了广泛的高速恒星。该项目的目标是了解大规模失控和 HVS 的起源和性质。这需要定量光谱和天体测量/运动学分析的结合。我们团队改进的模型大气和新颖的光谱诊断工具将应用于高保真光谱，部分已经在手头。盖亚天体测量将成为该项目的支柱。例如，这些数据可用于改进银河质量模型并追溯恒星轨迹至其起源地。此外，还可以建立完整的高速恒星样本来测试星群合成模型。起源地以及弹射机制将通过化学标记结合盖亚天体测量的信息来识别。