Stellar dynamics. The fastest unbound star in our Galaxy ejected by a thermonuclear supernova.
Hypervelocity stars (HVSs) travel with velocities so high that they exceed the escape velocity of the Galaxy. Several acceleration mechanisms have been discussed. Only one HVS (US 708, HVS 2) is a compact helium star. Here we present a spectroscopic and kinematic analysis of US 708. Traveling with a velocity of ~1200 kilometers per second, it is the fastest unbound star in our Galaxy. In reconstructing its trajectory, the Galactic center becomes very unlikely as an origin, which is hardly consistent with the most favored ejection mechanism for the other HVSs. Furthermore, we detected that US 708 is a fast rotator. According to our binary evolution model, it was spun-up by tidal interaction in a close binary and is likely to be the ejected donor remnant of a thermonuclear supernova.
European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany. Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics, Astronomical Institute, Friedrich-Alexander University Erlangen-Nuremberg, Sternwartstraße 7, 96049 Bamberg, Germany. sgeier@eso.org.
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Geier
Space Radiation Lab, MC 290-17 Cahill, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
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Fürst
Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics, Astronomical Institute, Friedrich-Alexander University Erlangen-Nuremberg, Sternwartstraße 7, 96049 Bamberg, Germany.
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Ziegerer
Department of Astrophysics/Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, Netherlands.
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Kupfer
Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics, Astronomical Institute, Friedrich-Alexander University Erlangen-Nuremberg, Sternwartstraße 7, 96049 Bamberg, Germany.
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Heber
Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics, Astronomical Institute, Friedrich-Alexander University Erlangen-Nuremberg, Sternwartstraße 7, 96049 Bamberg, Germany.
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Irrgang
Key Laboratory of the Structure and Evolution of Celestial Objects, Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, China.
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Wang
Key Laboratory of the Structure and Evolution of Celestial Objects, Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, China. Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany.
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Liu
Key Laboratory of the Structure and Evolution of Celestial Objects, Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, China.
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Han
Division of Physics, Mathematics, and Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA. Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany.
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Sesar
Division of Physics, Mathematics, and Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
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Levitan
Astrophysics Research Center, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK.
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Kotak
Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
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Magnier
Astrophysics Research Center, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK.
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Smith
Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
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Burgett
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany.
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Chambers
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany.
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Flewelling
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany.
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Kaiser
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany.
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Wainscoat
Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
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Waters