Origin of a Massive Hyper-runaway Subgiant Star LAMOST-HVS1: Implication from Gaia and Follow-up Spectroscopy
Origin of a Massive Hyper-runaway Subgiant Star LAMOST-HVS1: Implication from Gaia and Follow-up Spectroscopy
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DOI：
10.3847/1538-4357/ab05c8
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发表时间：
2018-10
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影响因子：
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通讯作者：
Kohei Hattori;M. Valluri;N. Castro;I. Roederer;G. Mahler;G. Khullar
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作者：
Kohei Hattori;M. Valluri;N. Castro;I. Roederer;G. Mahler;G. Khullar
我们报告LAMOST-HVS 1是一颗质量为8.3的超逃逸亚巨星星星，根据盖亚数据发布2（DR 2）和高分辨率光谱学的自行数据，它于2033年前从银河系的内恒星盘中以内禀抛射速度（修正了盘的流运动）抛射出来。极大的抛射速度表明这颗星星并不是被双星伴星的超新星爆炸抛射出来的。相反，它可能是在高密度环境中与更大质量的物体发生三体或四体动力学相互作用而被弹射出来的。这样的高密度环境可以在质量为104的年轻大质量星系团（YMC）的核心区域获得。参与LAMOST-HVS 1抛射的抛射剂可能是一个中等质量黑洞（100）、一颗超大质量星星（100）或多颗普通大质量恒星（1030）。根据LAMOST-HVS 1的飞行时间和抛射位置，我们认为其抛射剂或其纳塔尔星星团目前位于Norma旋臂附近，LAMOST-HVS 1的纳塔尔星星团可能是Norma旋臂附近的一个未被发现的YMC。
We report that LAMOST-HVS1 is a massive hyper-runaway subgiant star with a mass of 8.3 and super-solar metallicity, which was ejected from the inner stellar disk of the Milky Way ∼33 ago with the intrinsic ejection velocity of (corrected for the streaming motion of the disk), based on the proper motion data from Gaia Data Release 2 (DR2) and high-resolution spectroscopy. The extremely large ejection velocity indicates that this star was not ejected by the supernova explosion of a binary companion. Rather, it was probably ejected by a three- or four-body dynamical interaction with more massive objects in a high-density environment. Such a high-density environment may be attained at the core region of a young massive cluster (YMC) with mass of ≳104 . The ejection agent that took part in the ejection of LAMOST-HVS1 may be an intermediate mass black hole (≳100 ), a very massive star (≳100 ), or multiple ordinary massive stars (≳30 ). Based on the flight time and the ejection location of LAMOST-HVS1, we argue that its ejection agent or its natal star cluster is currently located near the Norma spiral arm. The natal star cluster of LAMOST-HVS1 may be an undiscovered YMC near the Norma spiral arm.