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Numerical simulations and infrared spectro-interferometry reveal the wind collision region in γ^2 Velorum

Lamberts, A. and Millour, F. and Liermann, A. and Dessart, L. and Driebe, T. and Duvert, G. and Finsterle, W. and Girault, V. and Massi, F. and Petrov, R. G. and Schmutz, W. and Weigelt, G. and Chesneau, O. (2017) Numerical simulations and infrared spectro-interferometry reveal the wind collision region in γ^2 Velorum. Monthly Notices of the Royal Astronomical Society, 468 (3). pp. 2655-2671. ISSN 0035-8711.

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Colliding stellar winds in massive binary systems have been studied through their radio, optical lines and strong X-ray emission for decades. More recently, near-infrared spectro-interferometric observations have become available in a few systems, but isolating the contribution from the individual stars and the wind collision region still remains a challenge. In this paper, we study the colliding wind binary γ^2 Velorum and aim at identifying the wind collision zone from infrared interferometric data, which provide unique spatial information to determine the wind properties. Our analysis is based on multi-epoch Very Large Telescope Interferometer/Astronomical Multi-BEam Recombiner (VLTI/AMBER) data that allows us to separate the spectral components of both stars. First, we determine the astrometric solution of the binary and confirm previous distance measurements. We then analyse the spectra of the individual stars, showing that the O star spectrum is peculiar within its class. Then, we perform three-dimensional hydrodynamic simulations of the system from which we extract model images, visibility curves and closure phases that can be directly compared with the observed data. The hydrodynamic simulations reveal the 3D spiral structure of the wind collision region, which results in phase-dependent emission maps. Our model visibility curves and closure phases provide a good match when the wind collision region accounts for 3–10 per cent γ^2 Vel's total flux in the near-infrared. The dialogue between hydrodynamic simulations, radiative transfer models and observations allows us to fully exploit the observations. Similar efforts will be crucial to study circumstellar environments with the new generation of VLTI instruments like GRAVITY and MATISSE.

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Lamberts, A.0000-0001-8740-0127
Alternate Title:Numerical simulations and infrared spectro-interferometry reveal the wind collision region in gamma2 Velorum
Additional Information:© 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 March 7. Received 2017 February 28; in original form 2016 December 26. Published: 22 March 2017. We thank the Centre National de la Recherche Scientifique (CNRS) for providing us with guaranteed time observations and the ‘Programme National de Physique Stellaire’ (PNPS) of the CNRS for continuous support during the years of preparation for this article. This work made use of the Jean-Marie Mariotti Center and Centre de Données astronomiques de Strasbourg tools. The MCMC orbital solution computations were performed on the ‘Mesocentre SIGAMM’ machine, hosted by Observatoire de la Côte d'Azur. Hydrodynamic numerical calculations were run on University of Wisconsin-Milwaukee supercomputer Avi and supercomputer Pleiades from the National Aeronautics and Space Administration (NASA) Supercomputing Division. Support for A. Lamberts was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G and National Science Foundation Collaborative Research Grant 1411920 and CAREER grant 1455342.
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:methods: numerical – techniques: interferometric – binaries: spectroscopic – stars: individual: γ2 Velorum – stars: winds, outflows – stars: Wolf–Rayet
Issue or Number:3
Record Number:CaltechAUTHORS:20170623-135643478
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Official Citation:A. Lamberts, F. Millour, A. Liermann, L. Dessart, T. Driebe, G. Duvert, W. Finsterle, V. Girault, F. Massi, R. G. Petrov, W. Schmutz, G. Weigelt, O. Chesneau; Numerical simulations and infrared spectro-interferometry reveal the wind collision region in γ2 Velorum. Mon Not R Astron Soc 2017; 468 (3): 2655-2671. doi: 10.1093/mnras/stx588
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78523
Deposited By: Tony Diaz
Deposited On:26 Jun 2017 20:31
Last Modified:03 Oct 2019 18:09

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