Characterizing the high-velocity stars of RAVE : the discovery of a metal-rich halo star born in the Galactic disc

Hawkins, Keith (Astrophysicist); Kordopatis, Georges, 1985-; Gilmore, Gerry, 1951-; Masseron, Thomas, 1978-; Wyse, Rosemary F. G.; Ruchti, Gregory R.; Bienaymé, Olivier; Bland-Hawthorn, J. (Joss); Boeche, Corrado; Freeman, Ken, 1940-; Gibson, Brad K.; Grebel, Eva K.; Helmi, A. (Amina), 1970-; Kunder, A. (Andrea); Munari, Ulisse; Navarro, Julio F. (Julio Fernando); Parker, Quentin A.; Reid, Warren A. (Warren Alfred); Scholz, Ralf-Dieter; Seabroke, George; Siebert, Arnaud, 1974-; Steinmetz, Matthias, 1966-; Watson, Fred (F. G.); Zwitter, Tomaž

Galaxy : abundances; Galaxy : halo; Galaxy : kinematics and dynamics
2015

Journal article


Rights
© 2015 The Authors
Abstract

We aim to characterize high-velocity (HiVel) stars in the solar vicinity both chemically and kinematically using the fourth data release of the RAdial Velocity Experiment (RAVE). We used a sample of 57 HiVel stars with Galactic rest-frame velocities larger than 275 km s−1. With 6D position and velocity information, we integrated the orbits of the HiVel stars and found that, on average, they reach out to 13 kpc from the Galactic plane and have relatively eccentric orbits consistent with the Galactic halo. Using the stellar parameters and [α/Fe] estimates from RAVE, we found the metallicity distribution of the HiVel stars peak at [M/H] = −1.2 dex and is chemically consistent with the inner halo. There are a few notable exceptions that include a hypervelocity star candidate, an extremely HiVel bound halo star, and one star that is kinematically consistent with the halo but chemically consistent with the disc. High-resolution spectra were obtained for the metal-rich HiVel star candidate and the second highest velocity star in the sample. Using these high-resolution data, we report the discovery of a metal-rich halo star that has likely been dynamically ejected into the halo from the Galactic thick disc. This discovery could aid in explaining the assembly of the most metal-rich component of the Galactic halo.

Publisher
The University of Hull
Peer reviewed
Yes
Language
English
Extent
1 MB
Identifier
hull:12800

Journal

Journal title
Monthly notices of the Royal Astronomical Society
Publication date
2015
Publisher
Oxford University Press
DOI
10.1093/mnras/stu2574
ISSN (Print)
0035-8711
ISSN (Electronic)
1365-2966
Volume
447
Issue
2
Start page
2046
End page
2058
Notes

This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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