The variability of the BRITE-est Wolf-Rayet binary, γ2 Velorum-I. Photometric and spectroscopic evidence for colliding winds

Author(s): Noel D. Richardson, Christopher M. P. Russell, Lucas St-Jean, Anthony F J Moffat, Nicole St-Louis, Tomer Shenar, Herbert Pablo, Grant M. Hill, Tahina Ramiaramanantsoa, Michael Corcoran, Kenji Hamuguchi, Thomas Eversberg, Brent Miszalski, André-Nicolas Chené, Wayne L. Waldron, Enrico J. Kotze, Marissa M. Kotze, Paul Luckas, Paulo Cacella, Bernard Heathcote, Jonathan Powles, Terry Bohlsen, Malcolm Locke, Gerald Handler, Rainer Kuschnig, Andrzej Pigulski, Adam Popowicz, Gregg A. Wade, Werner Wolfgang Weiss
Abstract: We report on the first multi-colour precision light curve of the bright Wolf-Rayet binary γ² Velorum, obtained over six months with the nanosatellites in the BRITE-Constellation fleet. In parallel, we obtained 488 high-resolution optical spectra of the system. In this first report on the data sets, we revise the spectroscopic orbit and report on the bulk properties of the colliding winds. We find a dependence of both the light curve and excess emission properties that scales with the inverse of the binary separation. When analysing the spectroscopic properties in combination with the photometry, we find that the phase dependence is caused only by excess emission in the lines, and not from a changing continuum. We also detect a narrow, high-velocity absorption component from the He I λ5876 transition, which appears twice in the orbit. We calculate smoothed-particle hydrodynamical simulations of the colliding winds and can accurately associate the absorption from He I to the leading and trailing arms of the wind shock cone passing tangentially through our line of sight. The simulations also explain the general strength and kinematics of the emission excess observed in wind lines such as C III λ5696 of the system. These results represent the first in a series of investigations into the winds and properties of γ² Velorum through multi-technique and multi-wavelength observational campaigns.
Organisation(s): Department of Astrophysics
External organisation(s): National Aeronautics & Space Administration (NASA), University of Montreal, W. M. Keck Observatory, Catholic University of America, Schnörringen Telescope Science Institute, Universität Potsdam, South African Astronomical Observatory (SAAO), Gemini Observatory, Eureka Scientific Inc., University of Western Australia, Southern Astro Spectroscopy Email Ring, Polish Academy of Sciences, Technische Universität Graz, Silesian University of Technology, University of Wrocław, Royal Military College of Canada
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 471
Pages: 2715 - 2729
No. of pages: 15
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stx1731
Publication date: 11-2017
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/3bb3fe1b-0d08-420d-8886-083a2c9deb29

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