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Discovery of a nearby 1700 km/s star ejected from the Milky Way by Sgr A*

Koposov, Sergey E, Boubert, Douglas, Li, Ting S, Erkal, Denis, Da Costa, Gary S, Zucker, Daniel B, Ji, Alexander P, Kuehn, Kyler, Lewis, Geraint F, Mackey, Dougal , Simpson, Jeffrey D, Shipp, Nora, Wan, Zhen, Belokurov, Vasily, Bland-Hawthorn, Joss, Martell, Sarah L, Nordlander, Thomas, Pace, Andrew B, De Silva, Gayandhi M and Wang, Mei-Yu (2020) Discovery of a nearby 1700 km/s star ejected from the Milky Way by Sgr A* Monthly Notices of the Royal Astronomical Society, 491 (2). pp. 2465-2480.

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Abstract

We present the serendipitous discovery of the fastest main-sequence hyper-velocity star (HVS) by the Southern Stellar Stream Spectroscopic Survey (S5). The star S5-HVS1 is a ∼2.35 M⊙ A-type star located at a distance of ∼9 kpc from the Sun and has a heliocentric radial velocity of 1017 ± 2.7 kms−1 without any signature of velocity variability. The current 3D velocity of the star in the Galactic frame is 1755 ± 50 kms−1⁠. When integrated backwards in time, the orbit of the star points unambiguously to the Galactic Centre, implying that S5-HVS1 was kicked away from Sgr A* with a velocity of ∼1800 kms−1 and travelled for 4.8 Myr to its current location. This is so far the only HVS confidently associated with the Galactic Centre. S5-HVS1 is also the first hyper-velocity star to provide constraints on the geometry and kinematics of the Galaxy, such as the Solar motion Vy,⊙ = 246.1 ± 5.3 kms−1 or position R0 = 8.12 ± 0.23 kpc. The ejection trajectory and transit time of S5-HVS1 coincide with the orbital plane and age of the annular disc of young stars at the Galactic Centre, and thus may be linked to its formation. With the S5-HVS1 ejection velocity being almost twice the velocity of other hyper-velocity stars previously associated with the Galactic Centre, we question whether they have been generated by the same mechanism or whether the ejection velocity distribution has been constant over time.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
NameEmailORCID
Koposov, Sergey E
Boubert, Douglas
Li, Ting S
Erkal, Denisd.erkal@surrey.ac.uk
Da Costa, Gary S
Zucker, Daniel B
Ji, Alexander P
Kuehn, Kyler
Lewis, Geraint F
Mackey, Dougal
Simpson, Jeffrey D
Shipp, Nora
Wan, Zhen
Belokurov, Vasily
Bland-Hawthorn, Joss
Martell, Sarah L
Nordlander, Thomas
Pace, Andrew B
De Silva, Gayandhi M
Wang, Mei-Yu
Date : January 2020
DOI : 10.1093/mnras/stz3081
Copyright Disclaimer : This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2019 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords : Stars: kinematics and dynamics; Galaxy: centre; Galaxy: fundamental parameters
Depositing User : Diane Maxfield
Date Deposited : 13 Jan 2020 15:27
Last Modified : 13 Jan 2020 15:27
URI: http://epubs.surrey.ac.uk/id/eprint/853317

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