DESI DR1中的中等质量逃逸星与超高速星候选体
Intermediate-mass runaway and hypervelocity star candidates in DESI DR1
- Universität Potsdam（波茨坦大学）
- Friedrich-Alexander University Erlangen-Nuremberg（埃尔朗根-纽伦堡大学）
机构由 AI 辅助整理，请以论文原文为准。
中文总结 AI 辅助
本研究基于DESI DR1数据搜寻极端速度星，识别出8颗河外起源的不受束缚恒星、11颗存疑的HVS候选体及26颗主序逃逸星，为相关天体物理问题提供约束。
中文摘要 AI 辅助
从银盘抛射出的逃逸星具有不同的速度范围，其中两个极端状态尤为受关注：超逃逸星的速度接近当地银河系逃逸速度，且仍受银河系引力束缚；超高速星（HVS）的速度超过逃逸速度，在形式上不受银河系引力束缚。研究这两类星可为星团形成、大质量双星的超新星爆发以及恒星晕的形状提供严格约束。本文利用暗能量光谱仪第一数据释放（DESI DR1）的数据，对这类极端速度星开展光谱搜寻。由于这类天体通常位于盖亚（Gaia）视差不可靠的距离范围之外，我们通过光谱与光谱能量分布（SEDs）的联合分析推导恒星参数，再将这些参数与恒星演化轨迹对比以推断距离，进而计算候选体的运动学特性。我们识别出8颗看似不受银河系引力束缚、可能起源于河外的恒星，这些恒星的投影旋转速度超过50 km s⁻¹，符合主序星的特征；另有11颗在假设为主序星的前提下被认定为潜在HVS候选体，但该解释未得到其旋转速度的支持，故其不受束缚的状态可信度较低；最后，26颗恒星显示出从银盘抛射出的主序逃逸星的证据。样本中最快的天体是一颗贫金属HVS候选体，其银心速度上限为934±110 km s⁻¹；测得径向速度最大的恒星为513 km s⁻¹，极可能是一颗慢脉动B型逃逸星。
英文摘要
Runaway stars ejected from the Galactic disc span a range of velocities, with two extreme regimes of particular interest. Hyper-runaway stars reach velocities approaching the local Galactic escape speed while remaining gravitationally bound to the Galaxy, while hypervelocity stars (HVS) have speeds which exceed the escape speed, leaving them formally unbound. Studying both populations places stringent constraints on star cluster formation, supernova explosions in massive binaries, and the shape of the stellar halo. Here we present a spectroscopic search for such extreme-velocity stars using data from the first data release of the Dark Energy Spectroscopic Instrument (DESI DR1). Because these objects are typically located at distances beyond the range where \textit{gaia} parallaxes are reliable, we derive stellar parameters through a combined analysis of spectroscopy and spectral energy distributions (SEDs). These parameters are then compared with stellar evolutionary tracks to infer distances, which are subsequently used to compute the kinematics of the candidates. We identify a sub-sample of eight stars that appear unbound to the Galaxy, likely of extragalactic origin. These stars exhibit projected rotational velocities exceeding $50$ km s$^{-1}$, consistent with a main-sequence nature. An additional eleven stars are identified as potential HVS candidates under the assumption that they are main-sequence stars. This interpretation is not supported by their rotational velocities, making their unbound status less secure. Finally, $26$ stars show evidence of being main-sequence runaway stars ejected from the Galactic disc. The fastest object in the sample is a metal-poor HVS candidate with a Galactocentric velocity upper-limit of $934 \pm 110$ km s$^{-1}$. The star with the largest measured radial velocity of $513$ km s$^{-1}$ is most likely a slowly pulsating B-type runaway star.
