Large-scale magnetic topologies of early M dwarfs
By J. Morin, J. Donati, P. Petit, X. Delfosse, T. Forveille, L. Albert, M. Aurière, R. Cabanac, B. Dintrans, R. Fares and 6 more. 2008
223 citations recorded by the source corpus.
We present here additional results of a spectropolarimetric survey of a small sample of stars ranging from spectral type M0 to M8 aimed at investigating observationally how dynamo processes operate in stars on both sides of the full convection threshold (spectral type M4). 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. This abrupt change in the large-scale magnetic topologies of M dwarfs (occurring at spectral type M3) has no related signature on X-ray luminosities (measuring the total amount of magnetic flux); it thus suggests that underlying dynamo processes become more efficient at producing large-scale fields (despite producing the same flux) at spectral types later than M3. We suspect that this change relates to the rapid decrease in the radiative cores of low-mass stars and to the simultaneous sharp increase of the convective turnover times (with decreasing stellar mass) that models predict to occur at M3; it may also be (at least partly) responsible for the reduced magnetic braking reported for fully convective stars. Based on observations obtained at the Telescope Bernard Lyot (TBL), operated by the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique of France. E-mail: donati@ast.obs-mip.fr (J-FD); jmorin@ast.obs-mip.fr (JM); petit@ast.obs-mip.fr (PP); xavier.delfosse@obs.ujf-grenoble.fr (XD); thierry.forveille@obs.ujf-grenoble.fr (TF); auriere@ast.obs-mip.fr (MA); remi.cabanac@ast.obs-mip.fr (RC); dintrans@ast.obs-mip.fr (BD); rfares@ast.obs-mip.fr (RF); tgastine@ast.obs-mip.fr (TG); mmj@st-and.ac.uk (MMJ); lignieres@ast.obs-mip.fr (FL); fpaletou@ast.obs-mip.fr (FP); julio.ramirez@obspm.fr (JCRV); sylvie.theado@ast.obs-mip.fr (ST)
Subfields: Astronomy and Astrophysics
View Paper: https://www.semanticscholar.org/paper/f4869f50e976fe22d53cc8e8da231abaea724b25
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In Astronomy and Astrophysics
Citations in the corpus
- KEPLER FLARES. I. ACTIVE AND INACTIVE M DWARFS (2014, background): “These results are consistent with the large scale magnetic structure model of Morin et al. (2008), which accounts for only a small fraction of the total magnetic energy in active mid-M stars; most of the energy is likely found in a large number of smaller active regions that are not detectable in…”
- Magnetic Fields of Nondegenerate Stars (2009, background): “…2006a; Morin et al. 2008a); additional observations of active mid-M dwarfs further confirmed that dynamo processes in fully-convectivstars with masses of about 0.3 M⊙ are apparently very successful at generating strong poloidal fields with simple axisymmetric configurations (Morin et al. 2008b).”
- Observations of Cool-Star Magnetic Fields (2012, methodology): “Results derived from time-series of Stokes V measurements are presented in Donati et al. (2008b) and Morin et al. (2008, 2010).”
- Large-scale magnetic topologies of late M dwarfs★: Magnetic topologies of late M dwarfs (2010, methodology): “From the analysis of a sample of early and mid M dwarfs Donati et al. (2008b) and Morin et al. (2008b) (hereafter D08 and M08b respectively) observed a strong change near the theoretical fullconvection threshold: while partly convective stars possess a weak non-axisymmetric field with a significant…”
- Stellar magnetism: empirical trends with age and rotation (2014, background): “…58: Ge et al. (2006); 59: Fares et al. (2012); 60: Fares et al. (2010); 61: Melo et al. (2006); 62: Donati et al. (2008a); 63: Vidotto et al. (2014); 64: Morin et al. (2008b); 65: Morin et al. (2010); 66: Schmitt, Fleming & Giampapa (1995); 67: Morin et al. (2008a); 68: Peres et al. (2000); 69:…”
- ON THE ANGULAR MOMENTUM EVOLUTION OF FULLY CONVECTIVE STARS: ROTATION PERIODS FOR FIELD M-DWARFS FROM THE MEarth TRANSIT SURVEY (2010, background): “In recent years, magnetic field measurements of stars on both sides of the fully-convective boundary have become available (e.g., Donati et al. 2008; Morin et al. 2008, 2010; Reiners & Basri 2009).”
- A CATALOG OF ROTATION AND ACTIVITY IN EARLY-M STARS (2012, background): “…of magnetically sensitive molecular lines (Reiners & Basri 2007; Shulyak et al. 2011), Zeeman Doppler imaging of M-stars (Donati et al. 2008; Morin et al. 2008) as well as numerical simulations of magnetic field generation in fully convective stars (Browning 2008) agree that strong magnetic…”