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

Jeffers, S. V. and Mengel, M. and Moutou, C. and Marsden, S. C. and Barnes, J. R. and Jardine, M. M. and Petit, P. and Schmitt, J. H. M. M. and See, V. and Vidotto, A. A. (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. ISSN 0035-8711

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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-scalemagnetic 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.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version deposited 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: 14 Feb 2019 03:21
Last Modified: 14 Feb 2019 04:26
Uncontrolled Keywords: polarimetric technique; τ Boo; magnetic field; solar-type; starspots
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/sty1717
URI: http://eprints.usq.edu.au/id/eprint/35724

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