论文标题
山丘机构和银河中心S-Star
The Hills Mechanism and the Galactic Center S-stars
论文作者
论文摘要
我们的银河中心包含年轻的恒星，包括从银河中心的0.05至0.5 PC之间的几百万年历史的顺时针磁盘，以及在〜0.01 PC的半乳酸中心距离处的B型恒星的S-Star群集。最近的观察结果表明，S-Star是顺时针磁盘中潮汐破坏二进制的残留物。特别是Koposov等。 2020年发现了一个从半河中心弹出的高速恒星5 Myr，其速度向量与磁盘一致。我们对这种二进制中断方案进行了详细研究。首先，我们量化了磁盘中二进制半轴轴的合理范围。这种二进制的动力蒸发由其他磁盘恒星而不是各向同性恒星种群主导。对于磁盘中半轴轴的预期范围，二进制潮汐破坏可以重现观察到的S-Star Semimajor轴分布。重现S-Star的观察到的热偏心分布需要额外的放松过程。 Koposov明星的飞行时间表明，此过程必须在10 MYR内生效。我们考虑三种可能性：（i）观察到的各向同性恒星簇的标量共振松弛，（ii）顺时针盘的扭矩，以及（iii）中间质量黑洞。我们得出的结论是，第一个和第三个机制足够快，可以再现观察到的S-Star偏心率分布。最后，我们表明，来自不等质量二进制的主要恒星将沉积在更大的半轴轴上，而不是次级轴，这可能解释了S-Stars中O恒星的缺乏。
Our Galactic center contains young stars, including the few million year old clockwise disk between 0.05 and 0.5 pc from the Galactic center, and the S-star cluster of B-type stars at a galactocentric distance of ~0.01 pc. Recent observations suggest the S-stars are remnants of tidally disrupted binaries from the clockwise disk. In particular, Koposov et al. 2020 discovered a hypervelocity star that was ejected from the Galactic center 5 Myr ago, with a velocity vector consistent with the disk. We perform a detailed study of this binary disruption scenario. First, we quantify the plausible range of binary semimajor axes in the disk. Dynamical evaporation of such binaries is dominated by other disk stars rather than by the isotropic stellar population. For the expected range of semimajor axes in the disk, binary tidal disruptions can reproduce the observed S-star semimajor axis distribution. Reproducing the observed thermal eccentricity distribution of the S-stars requires an additional relaxation process. The flight time of the Koposov star suggests that this process must be effective within 10 Myr. We consider three possibilities: (i) scalar resonant relaxation from the observed isotropic star cluster, (ii) torques from the clockwise disk, and (iii) an intermediate-mass black hole. We conclude that the first and third mechanisms are fast enough to reproduce the observed S-star eccentricity distribution. Finally, we show that the primary star from an unequal-mass binary would be deposited at larger semimajor axes than the secondary, possibly explaining the dearth of O stars among the S-stars.
