Journal Article

Two massive stars possibly ejected from NGC 3603 via a three-body encounter

V. V. Gvaramadze, A. Y. Kniazev, A.-N. Chené and O. Schnurr

in Monthly Notices of the Royal Astronomical Society: Letters

Published on behalf of The Royal Astronomical Society

Volume 430, issue 1, pages L20-L24
Published in print March 2013 |
Published online December 2012 | e-ISSN: 1745-3933 | DOI: http://dx.doi.org/10.1093/mnrasl/sls041

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We report the discovery of a bow-shock-producing star in the vicinity of the young massive star cluster NGC 3603 using archival data of the Spitzer Space Telescope. Follow-up optical spectroscopy of this star with Gemini-South led to its classification as O6 V. The orientation of the bow shock and the distance to the star (based on its spectral type) suggest that the star was expelled from the cluster, while the young age of the cluster (∼2 Myr) implies that the ejection was caused by a dynamical few-body encounter in the cluster’s core. The relative position on the sky of the O6 V star and a recently discovered O2 If*/WN6 star (located on the opposite side of NGC 3603) allows us to propose that both objects were ejected from the cluster via the same dynamical event – a three-body encounter between a single (O6 V) star and a massive binary (now the O2 If*/WN6 star). If our proposal is correct, then one can ‘weigh’ the O2 If*/WN6 star using the conservation of the linear momentum. Given a mass of the O6 V star of ≈30  M, we found that at the moment of ejection the mass of the O2 If*/WN6 star was ≈175  M. Moreover, the observed X-ray luminosity of the O2 If*/WN6 star (typical of a single star) suggests that the components of this originally binary system have merged (e.g., because of encounter hardening).

Keywords: stars: individual: WR 42e; stars: kinematics and dynamics; stars: massive; open clusters and associations: individual: NGC 3603

Journal Article.  3164 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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