Old, Metal-poor Extreme Velocity Stars in the Solar Neighborhood
Old, Metal-poor Extreme Velocity Stars in the Solar Neighborhood
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DOI：
10.3847/1538-4357/aadee5
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发表时间：
2018-05
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影响因子：
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通讯作者：
Kohei Hattori;M. Valluri;E. Bell;I. Roederer
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作者：
Kohei Hattori;M. Valluri;E. Bell;I. Roederer
我们报告在 Gaia-DR2 档案中发现了 30 颗具有极端空间速度 (≳480) 的恒星。这些恒星是 1743 颗恒星的子集，具有高精度视差、大切向速度 (vtan > 300 ) 以及 DR2 中测量的视线速度。通过追溯恒星过去的轨道，我们发现至少其中一颗恒星与被银河中心超大质量黑洞喷射出来的情况一致。另一颗恒星的轨道大约在 200 迈尔前经过大麦哲伦星云附近。与之前发现的蓝色超高速恒星不同，我们的样本缺乏金属（−1.5 1 ）。我们讨论将老恒星加速到如此极端速度的可能机制。相对于潜在的加速机制，观测到的该星群的高空间密度意味着这些恒星可能与银河系（MW）有关。如果它们是束缚的，发现这个种群将需要约 ∼600 的局部逃逸速度，因此意味着 MW 的维里质量为 M200 ∼ 1.4 × 1012M⊙。
We report the discovery of 30 stars with extreme space velocities (≳480 ) in the Gaia-DR2 archive. These stars are a subset of 1743 stars with high-precision parallax, large tangential velocity (vtan > 300 ), and measured line-of-sight velocity in DR2. By tracing the orbits of the stars back in time, we find at least one of them is consistent with having been ejected by the supermassive black hole at the Galactic Center. Another star has an orbit that passed near the Large Magellanic Cloud about 200 Myr ago. Unlike previously discovered blue hypervelocity stars, our sample is metal-poor (−1.5 1 ). We discuss possible mechanisms for accelerating old stars to such extreme velocities. The high observed space density of this population, relative to potential acceleration mechanisms, implies that these stars are probably bound to the Milky Way (MW). If they are bound, the discovery of this population would require a local escape speed of around ∼600 and consequently imply a virial mass of M200 ∼ 1.4 × 1012M⊙ for the MW.