Journal Article

Very massive runaway stars from three-body encounters

Vasilii V. Gvaramadze and Alessia Gualandris

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 410, issue 1, pages 304-312
Published in print January 2011 | ISSN: 0035-8711
Published online December 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17446.x
Very massive runaway stars from three-body encounters

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Very massive stars preferentially reside in the cores of their parent clusters and form binary or multiple systems. We study the role of tight very massive binaries in the origin of the field population of very massive stars. We performed numerical simulations of dynamical encounters between single (massive) stars and a very massive binary with parameters similar to those of the most massive known Galactic binaries, WR 20a and NGC 3603-A1. We found that these three-body encounters could be responsible for the origin of high peculiar velocities (≥70 km s−1) observed for some very massive (≥60–70 M) runaway stars in the Milky Way and the Large Magellanic Cloud (e.g. λ Cep, BD+43°3654, Sk −67°22, BI 237, 30 Dor 016), which can hardly be explained within the framework of the binary–supernova scenario. The production of high-velocity massive stars via three-body encounters is accompanied by the recoil of the binary in the opposite direction to the ejected star. We show that the relative position of the very massive binary R145 and the runaway early B-type star Sk−69°206 on the sky is consistent with the possibility that both objects were ejected from the central cluster, R136, of the star-forming region 30 Doradus via the same dynamical event – a three-body encounter.

Keywords: methods: numerical; binaries: general; stars: individual: λ Cep, BD+43°3654, Sk −67°22, BI 237, 30 Dor 016, HD269928; stars: kinematics and dynamics; galaxies: star clusters: individual: 30 Doradus

Journal Article.  6842 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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