Journal Article

On the origin of high-velocity runaway stars

Vasilii V. Gvaramadze, Alessia Gualandris and Simon Portegies Zwart

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 396, issue 1, pages 570-578
Published in print June 2009 | ISSN: 0035-8711
Published online June 2009 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2009.14809.x
On the origin of high-velocity runaway stars

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We explore the hypothesis that some high-velocity runaway stars attain their peculiar velocities in the course of exchange encounters between hard massive binaries and a very massive star (either an ordinary 50–100 M star or a more massive one, formed through runaway mergers of ordinary stars in the core of a young massive star cluster). In this process, one of the binary components becomes gravitationally bound to the very massive star, while the second one is ejected, sometimes with a high speed. We performed three-body scattering experiments and found that early B-type stars (the progenitors of the majority of neutron stars) can be ejected with velocities of ≳200–400 km s−1 (typical of pulsars), while 3–4 M stars can attain velocities of ≳300–400 km s−1 (typical of the bound population of halo late B-type stars). We also found that the ejected stars can occasionally attain velocities exceeding the Milky Ways's escape velocity.

Keywords: stellar dynamics; methods: N-body simulations; binaries: general; stars: individual: HD 271791; stars: neutron

Journal Article.  7187 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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