论文标题
盖亚时代的高速级星星。重新访问MMT调查中最极端的恒星
Hypervelocity Stars in the Gaia era. Revisiting the most extreme stars from the MMT survey
论文作者
论文摘要
在多个镜像望远镜（MMT）进行的高速恒星（HVS）调查确定了银河系中的42个B型恒星，其在银河静电架上的径向速度超过$+275 \，$ km $ $ $ \，$ km $ \，$ s $ s $ s $ {}^}^{ - 1} $。为了揭示这些高速离群值的性质和起源，需要它们完整的六维相空间信息。为此，我们从第二个数据释放的位置和适当的动作进行了补充{\ it gaia}的第二个数据释放，其径向速度和分光光度计距离基于对40个对象的可用MMT光谱的重新分析，并使用最先进的模型模型光谱和量身定制的分析策略。然后将37颗恒星的最终位置和速度向量用作随后的运动学研究的输入，以获得尽可能完整的图像。投影旋转速度，Kiel图中的位置和运动学特性的组合表明，除两个（B576，B598）以外的样品中的所有对象很可能是主要序列星。尽管可用的数据仍然不够精确，无法限制19个程序明星的原始地点，但我们确定了八个来自银河磁盘外边缘的对象，或者根本不是来自磁盘的外边缘，而十个可能源于银河系磁盘。对于或多或少约束空间起源的这18个目标中的几乎所有目标，银河中心（GC）被取消为可能的原产地。最值得注意的例外是B576，其起源与GC相吻合时，假设其具有蓝色的水平分支（BHB）性质。 HVS $ \，$ 22是迄今为止样本中最极端的对象。尽管它的起源是完全不受约束的，但GC从山丘机制中的弹射是最合理的解释，因为它当前的银河系休息速度$ 1530^{+690} _ { - 560} \，$ km $ $ \，$ km $ \，$ s $ s $ {}^{ - 1} $。
The hypervelocity star (HVS) survey conducted at the Multiple Mirror Telescope (MMT) identified 42 B-type stars in the Galactic halo whose radial velocity in the Galactic rest-frame exceeds $+275\,$km$\,$s${}^{-1}$. In order to unravel the nature and origin of those high-velocity outliers, their complete six-dimensional phase space information is needed. To this end, we complemented positions and proper motions from the second data release of {\it Gaia} with revised radial velocities and spectrophotometric distances that are based on a reanalysis of the available MMT spectra of 40 objects using state-of-the-art model spectra and a tailored analysis strategy. The resulting position and velocity vectors for 37 stars were then used as input for a subsequent kinematic investigation to obtain as complete a picture as possible. The combination of projected rotational velocity, position in the Kiel diagram, and kinematic properties suggests that all objects in the sample except two (B576, B598) are very likely to be main sequence stars. While the available data are still not precise enough to constrain the place of origin for 19 program stars, we identified eight objects that either come from the outer rim of the Galactic disk or not from the disk at all, along with ten that presumably stem from the Galactic disk. For almost all of those 18 targets with more or less well-constrained spatial origin, the Galactic center (GC) is disqualified as a possible place of origin. The most notable exception is B576, the origin of which coincides extremely well with the GC when assuming a blue horizontal branch (BHB) nature for it. HVS$\,$22 is by far the most extreme object in the sample. Although its origin is completely unconstrained, an ejection from the GC by the Hills mechanism is the most plausible explanation for its current Galactic rest-frame velocity of $1530^{+690}_{-560}\,$km$\,$s${}^{-1}$.
