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

K. Hawkins*, G. Kordopatis, G. Gilmore, T. Masseron, R. F. G. Wyse, G. Ruchti, O. Bienaymé, J. Bland-Hawthorn, C. Boeche, K. Freeman, B. K. Gibson, E. K. Grebel, A. Helmi, A. Kunder, U. Munari, J. F. Navarro, Q. A. Parker, W. A. Reid, R. D. Scholz, G. SeabrokeA. Siebert, M. Steinmetz, F. Watson, T. Zwitter

*Corresponding author for this work

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37 Citations (Scopus)
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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 57HiVel starswith 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.

Original languageEnglish
Pages (from-to)2046-2058
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume447
Issue number2
DOIs
Publication statusPublished - 21 Feb 2015

Bibliographical note

Copyright 2015 The Authors. First published in Monthly Notices of the Royal Astronomical Society, 447(2), 2046-2058. The original publication is available at http://doi.org/10.1093/mnras/stu2574, published by Oxford University Press on behalf of the Royal Astronomical Society. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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