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arXiv 2407.02593astro-ph.GAastro-ph.SR
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银河系极端速度恒星的详细化学研究

A Detailed Chemical Study of the Extreme Velocity Stars in the Galaxy

Tyler Nelson, Keith Hawkins, Henrique Reggiani, Diego Garza, Rosemary F. G. Wyse, Turner Woody

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16 pages, 7 figures
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AI总结：

本文通过对16颗候选晚型超高速恒星进行高分辨率光谱观测和化学丰度分析，结合运动学与轨道积分，发现其中仅一颗不受银河系束缚，且这些恒星在化学上均与恒星晕起源一致。

摘要：

二十多年过去了，对超高速恒星的研究仍处于起步阶段。这些恒星可以为银河系的总质量及其暗物质分布提供新的约束。然而，这些恒星是如何被加速到如此高的速度仍不清楚。已提出的各种产生机制可以通过化学动力学标记加以区分。Gaia和其他大型巡天的出现提供了数百个候选超高速天体，可作为地面高分辨率后续观测的目标。我们利用Apache Point Observatory和McDonald Observatory对16颗候选晚型超高速恒星进行了高分辨率光谱后续观测。我们推导了这些恒星的大气参数和化学丰度。我们测量了多达22种元素，包括以下核合成族：α元素（Mg、Si、Ca、Ti）、轻/奇Z元素（Na、Al、V、Cu、Sc）、铁峰元素（Fe、Cr、Mn、Co、Ni、Zn）以及中子俘获元素（Sr、Y、Zr、Ba、La、Nd、Eu）。我们的运动学分析显示，一颗候选恒星不受银河系束缚，两颗处于临界束缚状态，其余恒星受银河系束缚。最后，对于这三颗不受束缚或临界束缚的恒星，我们进行轨道积分以寻找可能的球状星团或矮星系前身天体。我们没有为这些恒星找到任何可能的候选系统，并得出结论：不受束缚的恒星很可能来自恒星晕，这与化学结果一致。其余受束缚的恒星在化学上也均与恒星晕一致。

英文摘要：

Two decades on, the study of hypervelocity stars is still in its infancy. These stars can provide novel constraints on the total mass of the Galaxy and its Dark Matter distribution. However how these stars are accelerated to such high velocities is unclear. Various proposed production mechanisms for these stars can be distinguished using chemo-dynamic tagging. The advent of Gaia and other large surveys have provided hundreds of candidate hyper velocity objects to target for ground based high resolution follow-up observations. We conduct high resolution spectroscopic follow-up observations of 16 candidate late-type hyper velocity stars using the Apache Point Observatory and the McDonald Observatory. We derive atmospheric parameters and chemical abundances for these stars. We measure up to 22 elements, including the following nucleosynthetic families: α (Mg, Si, Ca, Ti), light/Odd-Z (Na, Al, V, Cu, Sc), Fe-peak (Fe, Cr, Mn, Co, Ni, Zn), and Neutron Capture (Sr, Y, Zr, Ba, La, Nd, Eu). Our kinematic analysis shows one candidate is unbound, two are marginally bound, and the remainder are bound to the Galaxy. Finally, for the three unbound or marginally bound stars, we perform orbit integration to locate possible globular cluster or dwarf galaxy progenitors. We do not find any likely candidate systems for these stars and conclude that the unbound stars are likely from the the stellar halo, in agreement with the chemical results. The remaining bound stars are all chemically consistent with the stellar halo as well.

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