• DOI:10.1111/j.1365-2966.2008.13809.x
• Corpus ID: 11240756

Large-scale magnetic topologies of late M dwarfs⋆

@article{Morin2008LargescaleMT,
  title={Large-scale magnetic topologies of late M dwarfs⋆},
  author={Julien Morin and Jean-François Donati and Pascal Petit and Xavier Delfosse and Thierry Forveille and Loic Albert and Michel Auri{\`e}re and R{\'e}mi Cabanac and Boris Dintrans and R Fares and Thomas Gastine and Moira M. Jardine and François Lignières and F. Paletou and J. C. Ram{\'i}rez V{\'e}lez and Sylvie Th{\'e}ado},
  journal={arXiv: Astrophysics},
  year={2008},
  pages={2269-2286}
}

• J. Morin, J. Donati, +13 authors S. Théado
• Published 10 August 2008
• Physics
• arXiv: Astrophysics

We present here the final results of the first spectropolarimetric survey of a small sample of active M dwarfs, aimed at providing observational constraints on dynamo action on both sides of the full-convection threshold (spectral type M4). Our two previous studies (Donati et al. 2008b; Morin et al. 2008b) were focused on early and mid M dwarfs. The present paper examines 11 fully convective late M dwarfs (spectral types M5-M8). Tomographic imaging techniques were applied to time-series of circularly polarised profiles of 6 stars, in order to infer their large-scale magnetic topologies. For 3 other stars we could not produce such magnetic maps, because of low variability of the Stokes V signatures, but were able to derive some properties of the magnetic fields. We find 2 distinct categories of magnetic topologies: on the one hand strong axisymmetric dipolar fields (similar to mid M dwarfs), and on the other hand weak fields generally featuring a significant non-axisymmetric component, and sometimes a significant toroidal one. Comparison with unsigned magnetic fluxes demonstrates that the second category of magnetic fields shows less organization (less energy in the large scales), similarly to partly convective early M dwarfs. Stars in both categories have similar stellar parameters, our data do not evidence a separation between these 2 categories in the mass-rotation plane. We also report marginal detection of a large-scale magnetic field on the M8 star VB 10 featuring a significant toroidal axisymmetric component, whereas no field is detectable on VB 8 (M7).