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The relation between stellar magnetic field geometry and chromospheric activity cycles – II The rapid 120-day magnetic cycle of τ Bootis

Jeffers, S. V.; Mengel, M.; Moutou, C.; Marsden, S. C.; Barnes, J. R.; Jardine, M. M.; Petit, P.; Schmitt, J. H. M. M.; See, V.; Vidotto, A. A. and the BCool collaboration (2018). The relation between stellar magnetic field geometry and chromospheric activity cycles – II The rapid 120-day magnetic cycle of τ Bootis. Monthly Notices of the Royal Astronomical Society, 479(4) pp. 5266–5271.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1093/mnras/sty1717
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Abstract

One of the aims of the BCool programme is to search for cycles in other stars and to understand how similar they are to the Sun. In this paper, we aim to monitor the evolution of τ Boo’s large-scale magnetic field using high-cadence observations covering its chromospheric activity maximum. For the first time, we detect a polarity switch that is in phase with τ Boo’s 120-day chromospheric activity maximum and its inferred X-ray activity cycle maximum. This means that τ Boo has a very fast magnetic cycle of only 240 days. At activity maximum τ Boo’s large-scale field geometry is very similar to the Sun at activity maximum: it is complex and there is a weak dipolar component. In contrast, we also see the emergence of a strong toroidal component which has not been observed on the Sun, and a potentially overlapping butterfly pattern where the next cycle begins before the previous one has finished.

Item Type: Journal Item
Copyright Holders: 2018 The Authors
ISSN: 1365-2966
Keywords: techniques: polarimetric; stars: activity; stars: individual: (τ Boo); stars: magnetic field – stars: solar-type – starspots
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 56059
SWORD Depositor: Jisc Publications-Router
Depositing User: Jisc Publications-Router
Date Deposited: 07 Aug 2018 09:47
Last Modified: 02 May 2019 08:59
URI: http://oro.open.ac.uk/id/eprint/56059
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