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The Origin of HVS17, an Unbound Main Sequence B Star at 50 kpc

Brown, Warren R. and Cohen, Judith G. and Geller, Margaret J. and Kenyon, Scott J. (2013) The Origin of HVS17, an Unbound Main Sequence B Star at 50 kpc. Astrophysical Journal, 775 (1). Art. No. 32. ISSN 0004-637X.

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We analyze Keck Echellette Spectrograph and Imager spectroscopy of HVS17, a B-type star traveling with a Galactic rest frame radial velocity of +445 km s^(−1) in the outer halo of the Milky Way. HVS17 has the projected rotation of a main sequence B star and is chemically peculiar, with solar iron abundance and sub-solar alpha abundance. Comparing measured T_(eff) and log g with stellar evolution tracks implies that HVS17 is a 3.91 ± 0.09 M_☉, 153 ± 9 Myr old star at a Galactocentric distance of r = 48.5 ± 4.6 kpc. The time between its formation and ejection significantly exceeds 10 Myr and thus is difficult to reconcile with any Galactic disk runaway scenario involving massive stars. The observations are consistent, on the other hand, with a hypervelocity star ejection from the Galactic center. We show that Gaia proper motion measurements will easily discriminate between a disk and Galactic center origin, thus allowing us to use HVS17 as a test particle to probe the shape of the Milky Way's dark matter halo.

Item Type:Article
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URLURL TypeDescription Paper
Cohen, Judith G.0000-0002-8039-4673
Additional Information:© 2013 American Astronomical Society. Received 3 June 2013, accepted for publication 27 July 2013. Published 30 August 2013. This work was supported in part by the Smithsonian Institution. J. Cohen acknowledges partial support from AST–0908139. This research makes use of NASA’s Astrophysics Data System Bibliographic Services. We are grateful to the many people who have worked to make the Keck Telescopes and their instruments a reality, and who operate and maintain these observatories. The authors extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, none of the observations presented herein would have been possible. Facility: Keck:II (ESI)
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Smithsonian InstitutionUNSPECIFIED
Subject Keywords:Galaxy: center; Galaxy: halo; Galaxy: kinematics and dynamics; stars: early-type; stars: individual (SDSS J164156.39+472346.1)
Issue or Number:1
Record Number:CaltechAUTHORS:20131024-141234863
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Official Citation:The Origin of HVS17, an Unbound Main Sequence B Star at 50 kpc Warren R. Brown et al. 2013 ApJ 775 32
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42052
Deposited By: Ruth Sustaita
Deposited On:24 Oct 2013 21:34
Last Modified:03 Oct 2019 05:54

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