Stellar dynamics. The fastest unbound star in our Galaxy ejected by a thermonuclear supernova

S Geier; F Fürst; E Ziegerer; T Kupfer; U Heber; A Irrgang; B Wang; Z Liu; Z Han; B Sesar; D Levitan; R Kotak; E Magnier; K Smith; W S Burgett; K Chambers; H Flewelling; N Kaiser; R Wainscoat; C Waters

doi:10.1126/science.1259063

Stellar dynamics. The fastest unbound star in our Galaxy ejected by a thermonuclear supernova

Science. 2015 Mar 6;347(6226):1126-8. doi: 10.1126/science.1259063.

Authors

S Geier¹, F Fürst², E Ziegerer³, T Kupfer⁴, U Heber³, A Irrgang³, B Wang⁵, Z Liu⁶, Z Han⁵, B Sesar⁷, D Levitan⁸, R Kotak⁹, E Magnier¹⁰, K Smith⁹, W S Burgett¹⁰, K Chambers¹¹, H Flewelling¹¹, N Kaiser¹¹, R Wainscoat¹¹, C Waters¹⁰

Affiliations

¹ 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.
² Space Radiation Lab, MC 290-17 Cahill, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
³ Dr. Karl Remeis-Observatory and Erlangen Centre for Astroparticle Physics, Astronomical Institute, Friedrich-Alexander University Erlangen-Nuremberg, Sternwartstraße 7, 96049 Bamberg, Germany.
⁴ Department of Astrophysics/Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, Netherlands.
⁵ Key Laboratory of the Structure and Evolution of Celestial Objects, Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, China.
⁶ 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.
⁷ 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.
⁸ Division of Physics, Mathematics, and Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
⁹ Astrophysics Research Center, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK.
¹⁰ Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
¹¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany.

PMID: 25745168
DOI: 10.1126/science.1259063

Abstract

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.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.