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arXiv · 1807.00167

A new Hyper-Runaway star discovered from LAMOST and GAIA: ejected almost in the galactic rotation direction

Yin-Bi Li·A-Li Luo·Gang Zhao·You-Jun Lu·Xue-Sen Zhang·Fu-Peng Zhang·Bing Du·Fang Zuo·Lan Zhang·Yang Huang·Mao-Sheng Xiang·Jing-Kun Zhao·Yong-Heng Zhao·Zhan-Wen Hna
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Abstract

In this paper, we report the discovery of a new late-B type unbound hyper-runaway star (LAMOST-HVS4) from the LAMOST spectroscopic surveys. According to its atmospheric parameters, it is either a B-type main sequence (MS) star or a blue horizontal branch (BHB) star. Its Galactocentric distance and velocity are 30.3 +/- 1.6 kpc and 586 +/- 7 km/s if it is an MS star, and they are 13.2 +/- 3.7 kpc and 590 +/- 7 km/s if a BHB star. We track its trajectories back, and find that the trajectories intersect with the Galactic disk and the Galactic center lies outside of the intersection region at the 3 sigma confidence level. We investigate a number of mechanisms that could be responsible for the ejection of the star, and find that it is probably ejected from the Galactic disk by supernova explosion or multiple-body interactions in dense young stellar clusters.

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Yin-Bi Li, A-Li Luo, Gang Zhao, You-Jun Lu, Xue-Sen Zhang, Fu-Peng Zhang, Bing Du, Fang Zuo, Lan Zhang, Yang Huang, Mao-Sheng Xiang, Jing-Kun Zhao, Yong-Heng Zhao, Zhan-Wen Hna. 2018-06-30. A new Hyper-Runaway star discovered from LAMOST and GAIA: ejected almost in the galactic rotation direction. https://doi.org/10.3847/1538-3881%2Faad09a

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