Large-scale magnetic topologies of late 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

384 citations recorded by the source corpus.

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).

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/c7cff053d5b8a1447f29cf254f3939223d8e0984

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Citations in the corpus

Large-scale magnetic topologies of early M dwarfs (2008, background): “A similar conclusion is reached for V374 Peg (Donati et al. 2006a; Morin et al. 2008a); furthermore, M08 obtains that R⋆ sin i is equal to the predicted theoretical radius (within the error bars) for 4 other active stars, suggesting again that R⋆ is larger than expected.”
Magnetic cycles of the planet-hosting star τ Bootis – II. A second magnetic polarity reversal (2009, methodology): “Though not perfect, this procedure allows spectra to be secured with radial velocity (RV) precision of better than 30 ms−1 (Moutou et al. 2007; Morin et al. 2008).”
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…”
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…”
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).”
Searching for star–planet interactions within the magnetosphere of HD 189733 (2010, neutral): “Though not perfect, this procedure allows spectra to be secured with a radial velocity (RV) precision of better than 30 m s−1 (Moutou et al. 2007; Morin et al. 2008).”
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…”
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).”
Stellar winds on the main-sequence - II. The evolution of rotation and winds (2015, background): “…the properties of global photospheric magnetic fields appear to differ significantly between these two types of stars, both on the main-sequence (Morin et al. 2008) and on the pre-main-sequence (Gregory et al. 2012), and with the significantly different rotational evolution that has been…”
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).”
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:…”