Stellar magnetism: empirical trends with age and rotation

TY - JOUR

T1 - Stellar magnetism

T2 - empirical trends with age and rotation

AU - Vidotto, A. A.

AU - Gregory, S. G.

AU - Jardine, M.

AU - Donati, J. F.

AU - Petit, P.

AU - Morin, J.

AU - Folsom, C. P.

AU - Bouvier, J.

AU - Cameron, A. C.

AU - Hussain, G. A. J.

AU - Marsden, S.

AU - Waite, I. A.

AU - Fares, R.

AU - Jeffers, S.

AU - do Nascimento, J. D.

PY - 2014/7

Y1 - 2014/7

N2 - 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.

AB - 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.

KW - techniques: polarimetric

KW - stars: activity

KW - stars: evolution

KW - stars: magnetic field, planetary systems

KW - stars: rotation

UR - https://ui.adsabs.harvard.edu/abs/2014MNRAS.441.2361V/abstract

U2 - 10.1093/mnras/stu728

DO - 10.1093/mnras/stu728

M3 - Article

SN - 0035-8711

VL - 441

SP - 2361

EP - 2374

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 3

ER -