Large-scale magnetic topologies of mid M dwarfs

J. Morin, J. -F. Donati, P. Petit, X. Delfosse, T. Forveille, L. Albert, M. Auriere, R. Cabanac, B. Dintrans, R. Fares, T. Gastine, M. M. Jardine, F. Lignieres, F. Paletou, J. C. Ramirez Velez, S. Theado

Research output: Contribution to journalArticlepeer-review

269 Citations (Scopus)

Abstract

We present in this paper, the first results of a spectropolarimetric analysis of a small sample (similar to 20) of active stars ranging from spectral type M0 to M8, which are either fully convective or possess a very small radiative core. This study aims at providing new constraints on dynamo processes in fully convective stars.

This paper focuses on five stars of spectral type similar to M4, i.e. with masses close to the full convection threshold (similar or equal to 0.35 M-circle dot), and with short rotational periods. Tomographic imaging techniques allow us to reconstruct the surface magnetic topologies from the rotationally modulated time-series of circularly polarized profiles. We find that all stars host mainly axisymmetric large-scale poloidal fields. Three stars were observed at two different epochs separated by similar to 1 yr; we find the magnetic topologies to be globally stable on this time-scale.

We also provide an accurate estimation of the rotational period of all stars, thus allowing us to start studying how rotation impacts the large-scale magnetic field.

Original languageEnglish
Pages (from-to)567-581
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Volume390
DOIs
Publication statusPublished - 21 Oct 2008

Keywords

  • techniques : polarimetric
  • stars : activity
  • stars : low-mass, brown dwarfs
  • stars : magnetic fields
  • stars : rotation
  • LOW-MASS STARS
  • X-RAY-EMISSION
  • FULLY CONVECTIVE STAR
  • LOWER MAIN-SEQUENCE
  • COOL ACTIVE STARS
  • DIFFERENTIAL ROTATION
  • SPECTROPOLARIMETRIC OBSERVATIONS
  • BROWN DWARFS
  • SOLAR-TYPE
  • FIELD

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