Stellar magnetism: empirical trends with age and rotation

A. A. Vidotto, S. G. Gregory, M. Jardine, J. F. Donati, P. Petit, J. Morin, C. P. Folsom, J. Bouvier, A. C. Cameron, G. A. J. Hussain, S. Marsden, I. A. Waite, R. Fares, S. Jeffers, J. D. do Nascimento

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Abstract

We investigate how the observed large-scale surface magnetic fields of low-mass stars (̃0.1-2 M), reconstructed through Zeeman-Doppler imaging, vary with age t, rotation and X-ray emission. Our sample consists of 104 magnetic maps of 73 stars, from accreting pre-main sequence to main-sequence objects (1 Myr ≲ t ≲ 10 Gyr). For non-accreting dwarfs we empirically find that the unsigned average large-scale surface field is related to age as t-0.655 ± 0.045. This relation has a similar dependence to that identified by Skumanich, used as the basis for gyrochronology. Likewise, our relation could be used as an age-dating method (`magnetochronology'). The trends with rotation we find for the large-scale stellar magnetism are consistent with the trends found from Zeeman broadening measurements (sensitive to large- and small-scale fields). These similarities indicate that the fields recovered from both techniques are coupled to each other, suggesting that small- and large-scale fields could share the same dynamo field generation processes. For the accreting objects, fewer statistically significant relations are found, with one being a correlation between the unsigned magnetic flux and rotation period. We attribute this to a signature of star-disc interaction, rather than being driven by the dynamo.
Original languageEnglish
Pages (from-to)2361–2374
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Volume441
Issue number3
DOIs
Publication statusPublished - Jul 2014

Keywords

  • techniques: polarimetric
  • stars: activity
  • stars: evolution
  • stars: magnetic field, planetary systems
  • stars: rotation

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    Gregory, Scott

    • Physics - Lecturer in Astrophysics (joint appointment: 50% Mathematics 50% Physics)

    Person: Academic

    Cite this

    Vidotto, A. A., Gregory, S. G., Jardine, M., Donati, J. F., Petit, P., Morin, J., Folsom, C. P., Bouvier, J., Cameron, A. C., Hussain, G. A. J., Marsden, S., Waite, I. A., Fares, R., Jeffers, S., & do Nascimento, J. D. (2014). Stellar magnetism: empirical trends with age and rotation. Monthly Notices of the Royal Astronomical Society, 441(3), 2361–2374. https://doi.org/10.1093/mnras/stu728