%0 Journal Article
%T Do Non-dipolar Magnetic Fields Contribute to Spin-down Torques?
%+ University of St Andrews [Scotland]
%+ Département d'Astrophysique (ex SAP) (DAP)
%+ Institut de recherche en astrophysique et planétologie (IRAP)
%+ Institut für Astrophysik [Göttingen]
%+ University of Southern Queensland (USQ)
%+ Dublin Institute for Advanced Studies (DIAS)
%+ Centre d'Economie de l'Université Paris Nord (ancienne affiliation) (CEPN)
%+ Trinity College Dublin
%A See, Victor
%A Matt, Sean
%A Finley, Adam
%A Folsom, Colin, P.
%A Saikia, Sudeshna Boro
%A Donati, Jean-François
%A Fares, Rim
%A Hebrard, Élodie, M.
%A Jardine, Moira
%A Jeffers, Sandra, V.
%A Marsden, Stephen
%A Mengel, Matthew
%A Morin, Julien
%A Petit, Pascal
%A Vidotto, Aline
%A Waite, Ian
%< avec comité de lecture
%@ 0004-637X
%J The Astrophysical Journal
%I American Astronomical Society
%V 886
%N 2
%P 120
%8 2019-12-01
%D 2019
%Z 1910.02129
%Z 2019ApJ...886..120S
%R 10.3847/1538-4357/ab46b2
%K magnetohydrodynamics: MHD
%K stars: evolution
%K stars: low-mass
%K stars: magnetic field
%K stars: rotation
%K stars: winds
%K outflows
%Z Sciences of the Universe [physics]
%Z Sciences of the Universe [physics]/Astrophysics [astro-ph]
%Z Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR]Journal articles
%X Main-sequence low-mass stars are known to spin down as a consequence of their magnetized stellar winds. However, estimating the precise rate of this spin-down is an open problem. The mass-loss rate, angular momentum loss rate, and magnetic field properties of low-mass stars are fundamentally linked, making this a challenging task. Of particular interest is the stellar magnetic field geometry. In this work, we consider whether non-dipolar field modes contribute significantly to the spin-down of low-mass stars. We do this using a sample of stars that have all been previously mapped with Zeeman-Doppler imaging. For a given star, as long as its mass-loss rate is below some critical mass-loss rate, only the dipolar fields contribute to its spin-down torque. However, if it has a larger mass-loss rate, higher-order modes need to be considered. For each star, we calculate this critical mass-loss rate, which is a simple function of the field geometry. Additionally, we use two methods of estimating mass-loss rates for our sample of stars. In the majority of cases, we find that the estimated mass-loss rates do not exceed the critical mass-loss rate; hence, the dipolar magnetic field alone is sufficient to determine the spin-down torque. However, we find some evidence that, at large Rossby numbers, non-dipolar modes may start to contribute.
%G English
%L obspm-02399619
%U https://hal-obspm.ccsd.cnrs.fr/obspm-02399619
%~ OBSPM
%~ CEA
%~ INSU
%~ METEO
%~ UNIV-PARIS13
%~ UNIV-TLSE3
%~ CNRS
%~ CNES
%~ OMP
%~ OMP-IRAP
%~ DSM-IRFU
%~ IRFU-SAP
%~ CEPN
%~ DSV
%~ CEA-UPSAY
%~ USPC
%~ UNIV-PARIS-SACLAY
%~ CEA-UPSAY-SACLAY
%~ CEA-DRF
%~ CONDORCET3
%~ CAMPUS-CONDORCET
%~ SORBONNE-PARIS-NORD
%~ TEST-HALCNRS
%~ UNIV-UT3
%~ UT3-INP
%~ UT3-TOULOUSEINP
%~ TEST3-HALCNRS
%~ ACT-R