Abstract
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.
Original language | English |
---|---|
Article number | 120 |
Journal | Astrophysical Journal |
Volume | 886 |
Issue number | 2 |
DOIs | |
Publication status | Published - Dec 1 2019 |
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
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In: Astrophysical Journal, Vol. 886, No. 2, 120, 01.12.2019.
Research output: Contribution to journal › Article › peer-review
}
TY - JOUR
T1 - Do Non-dipolar Magnetic Fields Contribute to Spin-down Torques?
AU - See, Victor
AU - Matt, Sean P.
AU - Finley, Adam J.
AU - Folsom, Colin P.
AU - Saikia, Sudeshna Boro
AU - Donati, Jean Francois
AU - Fares, Rim
AU - Hébrard, Élodie M.
AU - Jardine, Moira M.
AU - Jeffers, Sandra V.
AU - Marsden, Stephen C.
AU - Mengel, Matthew W.
AU - Morin, Julien
AU - Petit, Pascal
AU - Vidotto, Aline A.
AU - Waite, Ian A.
N1 - Funding Information: Victor See Sean P. Matt Adam J. Finley Colin P. Folsom Sudeshna Boro Saikia Jean-Francois Donati Rim Fares �lodie M. H�brard Moira M. Jardine Sandra V. Jeffers Stephen C. Marsden Matthew W. Mengel Julien Morin Pascal Petit Aline A. Vidotto Ian A. Waite and the BCool Collaboration Victor See Sean P. Matt Adam J. Finley Colin P. Folsom Sudeshna Boro Saikia Jean-Francois Donati Rim Fares �lodie M. H�brard Moira M. Jardine Sandra V. Jeffers Stephen C. Marsden Matthew W. Mengel Julien Morin Pascal Petit Aline A. Vidotto Ian A. Waite and the BCool Collaboration University of Exeter, Department of Physics & Astronomy, Stocker Road, Devon, Exeter, EX4 4QL, UK Universit� de Toulouse, UPS-OMP, IRAP, Toulouse, France CNRS, Institut de Recherche en Astrophysique et Planetologie, 14, avenue Edouard Belin, F-31400 Toulouse, France University of Vienna, Department of Astrophysics, Tu�rkenschanzstrasse 17, 1180 Vienna, Austria Physics Department, United Arab Emirates University, P.O. Box 15551, Al-Ain, United Arab Emirates SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK Universit�t G�ttingen, Institut f�r Astrophysik, Friedrich-Hund-Platz 1, D-37077 G�ttingen, Germany University of Southern Queensland, Centre for Astrophysics, Toowoomba, QLD 4350, Australia Laboratoire Univers et Particules de Montpellier, Universit� de Montpellier, CNRS, F-34095, France School of Physics, Trinity College Dublin, University of Dublin, Dublin-2, Ireland Private astronomer. Victor See, Sean P. Matt, Adam J. Finley, Colin P. Folsom, Sudeshna Boro Saikia, Jean-Francois Donati, Rim Fares, �lodie M. H�brard, Moira M. Jardine, Sandra V. Jeffers, Stephen C. Marsden, Matthew W. Mengel, Julien Morin, Pascal Petit, Aline A. Vidotto, Ian A. Waite and and the BCool Collaboration 2019-12-01 2019-11-27 13:51:09 cgi/release: Article released bin/incoming: New from .zip Austrian Space Application Programme S11601-N16 Austrian Space Application Programme S11604-N16 German Science Foundation Research Unit JE 701/3-1 German Science Foundation Research Unit RE 1664/18 yes 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. � 2019. The American Astronomical Society. 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PY - 2019/12/1
Y1 - 2019/12/1
N2 - 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.
AB - 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.
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UR - http://www.scopus.com/inward/citedby.url?scp=85075304150&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/ab46b2
DO - 10.3847/1538-4357/ab46b2
M3 - Article
AN - SCOPUS:85075304150
SN - 0004-637X
VL - 886
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 120
ER -