Large-scale magnetic topologies of late M dwarfs★: Magnetic topologies of late M dwarfs

By J. Morin, J. Donati, P. Petit, X. Delfosse, T. Forveille, M. Jardine. 2010

342 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, Instrumentation

View Paper: https://www.semanticscholar.org/paper/3d6e10061749c9a6b71e80ba85f3dc8c014e778b

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In Astronomy and Astrophysics

1. A. Reiners
2. D. Charbonneau
3. James R. A. Davenport
4. J. Irwin
5. G. Basri
6. E. Newton
7. K. Luhman
8. Jon Fortney

In Instrumentation

1. A. Reiners
2. D. Charbonneau
3. G. Basri
4. James R. A. Davenport
5. E. Newton
6. J. Irwin
7. T. Reinhold
8. P. Nutzman

Citations in the corpus

• Rotation and differential rotation of active Kepler stars (2013, background): “This effect becomes even more important when stars become fully convective (Morin et al. 2010).”
• Improved angular momentum evolution model for solar-like stars II. Exploring the mass dependence (2015, neutral): “…magnetic topology is indeed suggested for main-sequence stars, with solar-mass stars having more multipolar magnetic structure than lower mass stars whose magnetic topology tends to be dipole dominated (Petit et al. 2008; Donati & Landstreet 2009; Morin et al. 2010; Gregory et al. 2012).”
• The stellar rotation–activity relationship in fully convective M dwarfs (2018, background): “…Hα (e.g. Hawley 1993; Mohanty & Basri 2003), coronal radio (White, Kundu & Jackson 1989), X-ray emission (Wright et al. 2011), and strong large-scale surface magnetic fields as evidenced by Zeeman broadening (Johns-Krull & Valenti 1996) and spectropolarimetry (Morin et al. 2010; See et al. 2015).”
• Stellar magnetism: empirical trends with age and rotation (2014, background): “Over-plotted to Figure 6 are the remaining M dwarf stars, without age estimates (open symbols), from the samples in Donati et al. (2008a) and Morin et al. (2008b, 2010).”
• Least-squares deconvolution of the stellar intensity and polarization spectra (2010, methodology): “This approach is frequently used in recent Doppler imaging studies of the stellar surface structure and magnetic fields (e.g., Donati et al. 2008; Morin et al. 2008; Folsom et al. 2008).”
• THE EVOLUTION OF CATACLYSMIC VARIABLES AS REVEALED BY THEIR DONOR STARS (2011, background): “Broadly speaking, there is evidence for systematic changes in both magnetic field strength and topology with spectral type (e.g., Reiners & Basri 2008, 2009, 2010; Donati et al. 2008; Morin et al. 2010).”
• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (2016, methodology): “Following Reiners & Basri (2009) and Morin et al. (2010) we take f1 = 0.2 if the large-scale component of the field is dipoledominated and f1 = 0.06 in the multipolar case.”
• KEPLER FLARES. I. ACTIVE AND INACTIVE M DWARFS (2014, background): “A series of papers reporting spectropolarimetric observations of M dwarfs (Morin et al. 2008; Donati et al. 2008; Morin et al. 2010) describes the change in the large-scale magnetic field structure between early M dwarfs that retain a radiative core, presumably have a solar-type dynamo and exhibit…”
• 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).”
• RADIUS-DEPENDENT ANGULAR MOMENTUM EVOLUTION IN LOW-MASS STARS. I (2011, background): “Additionally, the change in field topology in fully convective stars does not appear monotonic; stars later that 0.2 M appear to become less dipolar again, similar to solar-types and unlike fully convective stars with mass 0.2 M (Morin et al. 2010).”
• THE Hα EMISSION OF NEARBY M DWARFS AND ITS RELATION TO STELLAR ROTATION (2016, background): “Nevertheless, Zeeman Doppler imaging reveals that some do indeed have large-scale fields (Donati et al. 2008; Morin et al. 2010), and many mid-to-late M-dwarfs have strong signatures of magnetic activity, with emission from the X-ray to the radio (e.g. Berger et al. 2010; Stelzer et al. 2013).”
• Observations of Cool-Star Magnetic Fields (2012, methodology): “Including the results of Morin et al. (2010), Figure 23 shows properties of the large-scale magnetic geometries of cool stars from Donati (2011) in a visualization of magnetic field geometries as a function of mass and rotation period.”