Magnetic field and velocity of early M dwarfs

The present paper focuses on early M stars (M0-M3), that is above the full convection threshold. Applying tomographic imaging techniques to time series of rotationally modulated circularly polarized profiles collected with the NARVAL spectropolarimeter, we determine the rotation period and reconstruct the large-scale magnetic topologies of six early M dwarfs.

We find that early-M stars preferentially host large-scale fields with dominantly toroidal and non-axisymmetric poloidal configurations, along with significant differential rotation (and long-term variability); only the lowest-mass star of our subsample is found to host an almost fully poloidal, mainly axisymmetric large-scale field resembling those found in mid-M dwarfs.