Could a change in magnetic field geometry cause the break in the wind-activity relation?
Article
Article Title | Could a change in magnetic field geometry cause the break in the wind-activity relation? |
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ERA Journal ID | 41989 |
Article Category | Article |
Authors | Vidotto, A. A. (Author), Donati, J.-F. (Author), Jardine, M. (Author), See, V. (Author), Petit, P. (Author), Boisse, I. (Author), Boro Saikia, S. (Author), Hebrard, E. (Author), Jeffers, S. V. (Author), Marsden, S. C. (Author) and Morin, J. (Author) |
Journal Title | Monthly Notices of the Royal Astronomical Society: Letters |
Journal Citation | 455 (1), pp. L52-L56 |
Number of Pages | 5 |
Year | 2016 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 1745-3925 |
1745-3933 | |
Digital Object Identifier (DOI) | https://doi.org/10.1093/mnrasl/slv147 |
Web Address (URL) | https://academic.oup.com/mnrasl/article/455/1/L52/2589651 |
Abstract | Wood et al. suggested that mass-loss rate is a function of X-ray flux (M˙ ∝ F1.34 x ) for dwarf stars with Fx Fx,6 ≡ 106 erg cm−2 s−1. However, more active stars do not obey this relation. These authors suggested that the break at Fx,6 could be caused by significant changes in magnetic field topology that would inhibit stellar wind generation. Here, we investigate this hypothesis by analysing the stars in Wood et al. sample that had their surface magnetic fields reconstructed through Zeeman–Doppler Imaging (ZDI). Although the solar-like outliers in the M˙ – Fx relation have higher fractional toroidal magnetic energy, we do not find evidence of a sharp transition in magnetic topology at Fx,6. To confirm this, further wind measurements and ZDI observations at both sides of the break are required. As active stars can jump between states with highly toroidal to highly poloidal fields, we expect significant scatter in magnetic field topology to exist for stars with Fx Fx,6. This strengthens the importance of multi-epoch ZDI observations. Finally, we show that there is a correlation between Fx and magnetic energy, which implies that M˙ – magnetic energy relation has the same qualitative behaviour as the original M˙ – Fx relation. No break is seen in any of the Fx – magnetic energy relations. |
Keywords | magnetic fields – stars: activity – stars: coronae – stars: low-mass – stars: winds, outflows. |
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: Letters ©: 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Byline Affiliations | University of Geneva, Switzerland |
University of Toulouse, France | |
University of St Andrews, United Kingdom | |
Aix-Marseille University, France | |
Georg August University of Gottingen, Germany | |
Computational Engineering and Science Research Centre | |
University of Montpellier, France | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q3w30/could-a-change-in-magnetic-field-geometry-cause-the-break-in-the-wind-activity-relation
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Vidotto 2016 Monthly Notices of the Royal Astronomical Society Letters 455 L52-L56.pdf | ||
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