Temporal variability of the wind from the star τ Boötis

Nicholson, B. A. and Vidotto, A. A. and Mengel, M. and Brookshaw, L. and Carter, B. and Petit, P. and Marsden, S. C. and Jeffers, S. V. and Fares, R. and BCool Collaboration, (2016) Temporal variability of the wind from the star τ Boötis. Monthly Notices of the Royal Astronomical Society, 459 (2). pp. 1907-1915. ISSN 0035-8711

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We present new wind models for τ Bo¨otis(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.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version made accessible, in accordance with the copyright policy of the publisher.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences
Date Deposited: 06 Mar 2017 23:22
Last Modified: 17 Aug 2017 23:46
Uncontrolled Keywords: MHD; stars; individual; τ Bo¨otis; magnetic field; winds; outflows
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: 10.1093/mnras/stw731
URI: http://eprints.usq.edu.au/id/eprint/30369

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