arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.01655astro-ph.SR
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用LAMOST DR6和DR7光谱在盖亚DR2中识别的热亚矮星。II。运动学

Hot Subdwarf Stars Identified in Gaia DR2 with Spectra of LAMOST DR6 and DR7. II. Kinematics

Yangping Luo, Peter Nemeth, Qida Li

摘要:

结合LAMOST视向速度、Gaia弛豫和自行,给出了银河系的三维空间运动和182颗单线热亚矮星的轨道。这些恒星已经被Lei等人(2020)在Gaia DR2中用LAMOST DR6和DR7光谱识别出来。log(y)> 0的富氦热亚矮星显示出银河系速度分量和轨道参数的最大标准偏差,而-1 <log(y)<0的富氦热亚矮星显示出第二大标准偏差。log(y)<-1的两组缺氦星显示出相似的标准偏差,与富氦星相比,标准偏差系统地较低。根据它们在U-V速度图、J_z偏心率图和银河系轨道中的位置,给出了四个热亚矮星氦群的运动学布居分类。四个热亚矮星氦群在晕、薄盘和厚盘中的分数分布的总体趋势与Luo等报道的结果基本一致。(2019)基于LAMOST DR5,这似乎支持二元种群合成的预测(Han et al. 2003; 2008)。log(y)<-2.2的贫氦星可能起源于稳定的洛希瓣溢出通道,log(y)<-2.2的贫氦星可能起源于共同包层喷射通道,log(y)> 0的富氦星可能起源于双氦白矮星的合并通道。薄盘和晕中-1 <log(y)<0的富He热亚矮星的比例远高于厚盘,这意味着这些恒星在薄盘和晕中有不同的形成通道。

英文摘要:

Combining the LAMOST radial velocities with Gaia parallaxes and proper motions, we presented 3D Galactic space motions and the orbits of 182 single-lined hot subdwarf stars. These stars have been identified by Lei et al. (2020) in Gaia DR2 with LAMOST DR6 and DR7 spectra. He-rich hot subdwarf stars with log(y)>0 show the largest standard deviations of the Galactic velocity components and orbital parameters, while those with -1<log(y)<0 exhibit the second largest standard deviations. The two groups of He-deficient stars with log(y)<-1 show similar standard deviations, which is systematically lower compared to He-rich stars. We also presented a kinematic population classification of the four hot subdwarf helium groups based on their positions in the U-V velocity diagram, J_z-eccentricity diagram and their Galactic orbits. The overall tendency of the fractional distributions of the four hot subdwarf helium groups in the halo, thin disk and thick disk is largely consistent with the findings reported by Luo et al.(2019) based on LAMOST DR5, which appears to support the predictions of binary population synthesis (Han et al. 2003; 2008). He-deficient stars with -2.2<log(y)<-1 likely origin from stable the Roche lobe overflow channel, He-deficient stars with log(y)<-2.2 from the common envelope ejection channel, and He-rich stars with log(y)>0 from the merger channel of double He white dwarf stars. The fraction of He-rich hot subdwarf stars with -1<log(y)<0 in the thin disk and the halo are far higher than in the thick disk, which implies that these stars have different formation channels in the thin disk and in the halo.

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