Temporal variability of the wind from the star τ Boötis
Article
Article Title | Temporal variability of the wind from the star τ Boötis |
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ERA Journal ID | 1074 |
Article Category | Article |
Authors | Nicholson, B. A. (Author), Vidotto, A. A. (Author), Mengel, M. (Author), Brookshaw, L. (Author), Carter, B. (Author), Petit, P. (Author), Marsden, S. C. (Author), Jeffers, S. V. (Author) and Fares, R. (Author) |
Journal Title | Monthly Notices of the Royal Astronomical Society |
Journal Citation | 459 (2), pp. 1907-1915 |
Number of Pages | 9 |
Year | 2016 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 0035-8711 |
1365-2966 | |
Digital Object Identifier (DOI) | https://doi.org/10.1093/mnras/stw731 |
Web Address (URL) | https://academic.oup.com/mnras/article/459/2/1907/2595119 |
Abstract | We present new wind models for τ Boötis (τ Boo), a hot-Jupiter-host-star whose observable magnetic cycles makes it a uniquely useful target for our goal of monitoring the temporal variability of stellar winds and their exoplanetary impacts. Using spectropolarimetric observations from May 2009 to January 2015, the most extensive information of this type yet available, to reconstruct the stellar magnetic field, we produce multiple 3D magnetohydrodynamic stellar wind models. Our results show that characteristic changes in the large-scale magnetic field as the star undergoes magnetic cycles produce changes in the wind properties, both globally and locally at the position of the orbiting planet. Whilst the mass loss rate of the star varies by only a minimal amount (4 per cent), the rates of angular momentum loss and associated spin-down time-scales are seen to vary widely (up to 140 per cent), findings consistent with and extending previous research. In addition, we find that temporal variation in the global wind is governed mainly by changes in total magnetic flux rather than changes in wind plasma properties. The magnetic pressure varies with time and location and dominates the stellar wind pressure at the planetary orbit. By assuming a Jovian planetary magnetic field for τ Boo b, we nevertheless conclude that the planetary magnetosphere can remain stable in size for all observed stellar cycle epochs, despite significant changes in the stellar field and the resulting local space weather environment. |
Keywords | Individual; Magnetic field-stars; MHD-methods; Numerical-stars; Outflows; Winds; τ Boötis-stars |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
Public Notes | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Byline Affiliations | Computational Engineering and Science Research Centre |
University of Geneva, Switzerland | |
French National Centre for Scientific Research, France | |
University of Gottingen, Germany | |
National Institute of Astrophysics, Italy | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q3w2x/temporal-variability-of-the-wind-from-the-star-bo-tis
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