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Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2016

Could a change in magnetic field geometry cause the break in the wind-activity relation?

Résumé

Wood et al. suggested that mass-loss rate is a function of X-ray flux (M alpha F-x(1.34)) for dwarf stars with F-x less than or similar to F-x,(6) equivalent to 10(6) erg cm(-2) s(-1). However, more active stars do not obey this relation. These authors suggested that the break at F-x,(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 - F-x relation have higher fractional toroidal magnetic energy, we do not find evidence of a sharp transition in magnetic topology at F-x,(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 F-x greater than or similar to F-x,(6). This strengthens the importance of multi-epoch ZDI observations. Finally, we show that there is a correlation between F-x and magnetic energy, which implies that. M - magnetic energy relation has the same qualitative behaviour as the original. M - F-x relation. No break is seen in any of the F-x - magnetic energy relations.

Dates et versions

hal-01440120 , version 1 (19-01-2017)

Identifiants

Citer

A. A. Vidotto, J. -F. Donati, M. Jardine, V. See, P. Petit, et al.. Could a change in magnetic field geometry cause the break in the wind-activity relation?. Monthly Notices of the Royal Astronomical Society, 2016, 455 (1), pp.L52--L56. ⟨10.1093/mnrasl/slv147⟩. ⟨hal-01440120⟩
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