Magnetometry of M dwarfs: methodology & results

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1 Magnetometry of M dwarfs: methodology & results Julien Morin Laboratoire Univers et Particules de Montpellier First MaTYSSE meeting - Toulouse 2nd November 2015

2 Outline 1 Magnetic fields: a crucial ingredient of stellar physics 2 Detection and characterization of stellar magnetic fields 3 A brief overview of M dwarfs magnetism 4 Summary Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

3 Outline 1 Magnetic fields: a crucial ingredient of stellar physics Stellar magnetic fields are ubiquitous Stellar magnetic fields play a key role The origin of stellar magnetic fields 2 Detection and characterization of stellar magnetic fields 3 A brief overview of M dwarfs magnetism 4 Summary Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

(2006a) Wide variety of properties Intensity/geometry/variability V374 Peg,

4 Stellar magnetic fields are ubiquitous Measured across H-R diagram All masses All evolutionary stages τ Sco, 15 M Donati et al.(2006a) Wide variety of properties Intensity/geometry/variability V374 Peg, 0.3 M Donati et al.(2006b) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

strongest impact Jets launching Magnetospheric accretion Credit: F.

5 Magnetic fields play a key role (1/2) Activity Observable across electromagnetic spectrum Impact of B on all atmospheric layers Formation Phase where B has strongest impact Jets launching Magnetospheric accretion Credit: F. Espenak Credit: ESO Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

Magnetic fields play a key role (2/2) Rotation During formation star disc interaction Post T Tauri Magnetized winds Much more efficient than non-magnetized Schatzman (1962) Star planet

6 Magnetic fields play a key role (2/2) Rotation During formation star disc interaction Post T Tauri Magnetized winds Much more efficient than non-magnetized Schatzman (1962) Star planet interaction Stellar wind Coronal mass ejection Planetary magnetosphere Planetary atmosphere Credit: NASA / JPL-Caltech / R. Hurt Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

7 Magnetic fields play a key role (2/2) Rotation During formation star disc interaction Post T Tauri Magnetized winds Much more efficient than non-magnetized Schatzman (1962) Star planet interaction Stellar wind Coronal mass ejection Planetary magnetosphere Planetary atmosphere Credit: NASA / ESA Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

8 The origin of stellar magnetic fields (1/2) High-mass star: Simple steady field Fossil field? Partly convective star: Complex B temporal evolutions Solar-type dynamo Fully convective star: No tachocline Non-solar dynamo Adapted from Reiners (2008) star sketches credit J. Bennett et al. Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

9 The origin of stellar magnetic fields (1/2) High-mass star: Simple steady field Fossil field? Partly convective star: Complex B temporal evolutions Solar-type dynamo Fully convective star: No tachocline Non-solar dynamo Adapted from Reiners (2008) star sketches credit J. Bennett et al. Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

10 The origin of stellar magnetic fields (1/2) High-mass star: Simple steady field Fossil field? Partly convective star: Complex B temporal evolutions Solar-type dynamo Fully convective star: No tachocline Non-solar dynamo Adapted from Reiners (2008) star sketches credit J. Bennett et al. Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

11 The origin of stellar magnetic fields (1/2) High-mass star: Simple steady field Fossil field? Partly convective star: Complex B temporal evolutions Solar-type dynamo Fully convective star: No tachocline Non-solar dynamo Adapted from Reiners (2008) star sketches credit J. Bennett et al. Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

12 The origin of stellar magnetic fields (1/2) Adapted from Reiners (2008) star sketches credit J. Bennett et al. High-mass star: Simple steady field Fossil field? Partly convective star: Complex B temporal evolutions Solar-type dynamo Fully convective star: No tachocline Non-solar dynamo Relation parameters B properties? Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

poloidal toroidal Poloidal field regeneration?

13 The origin of stellar magnetic fields (2/2) Dynamo action Amplifies and sustains B Conversion E kin E mag Induction effect B t = (u B) }{{} induction + } η B {{ } dissipation Solar dynamo Ω-effect: poloidal toroidal Poloidal field regeneration? Role of tachocline Stellar magnetic fields Different regime of parameters Non-solar dynamo Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

14 The origin of stellar magnetic fields (2/2) Dynamo action Amplifies and sustains B Conversion E kin E mag Induction effect B t = (u B) }{{} induction + } η B {{ } dissipation Solar dynamo Ω-effect: poloidal toroidal Poloidal field regeneration? Role of tachocline Stellar magnetic fields Different regime of parameters Non-solar dynamo Adapted from figures by J. Braithwaite and T. Gastine Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

The origin of stellar magnetic fields (2/2) Dynamo action Amplifies and sustains B Conversion E kin E mag Induction effect B t = (u B) }{{} induction + } η B {{ } dissipation Solar dynamo Ω-effect:

15 The origin of stellar magnetic fields (2/2) Dynamo action Amplifies and sustains B Conversion E kin E mag Induction effect B t = (u B) }{{} induction + } η B {{ } dissipation Solar dynamo Ω-effect: poloidal toroidal Poloidal field regeneration? Role of tachocline Ω-effect Stellar magnetic fields Different regime of parameters Non-solar dynamo Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

16 The origin of stellar magnetic fields (2/2) Dynamo action Amplifies and sustains B Conversion E kin E mag Induction effect B t = (u B) }{{} induction + } η B {{ } dissipation Solar dynamo Ω-effect: poloidal toroidal Poloidal field regeneration? Role of tachocline Stellar magnetic fields Different regime of parameters Non-solar dynamo Internal angular velocity Shu et al., 2006; from SOHO MDI data Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

17 Outline 1 Magnetic fields: a crucial ingredient of stellar physics 2 Detection and characterization of stellar magnetic fields Indirect measurements: stellar activity Direct measurements of photospheric magnetic fields Zeeman-Doppler Imaging 3 A brief overview of M dwarfs magnetism 4 Summary Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

18 Indirect measurements: stellar activity Interaction B atmosphere Spots, plages Vis. photometry/spectroscopy Chromosphere, TR, corona Radio X-rays Usual proxies for stellar B Caii H&K emission Coronal X-ray emission cyclic variations Rotation activity relation Growth + saturation Rossby number : Ro = P rot τ c SOHO, EUV Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

19 Indirect measurements: stellar activity Interaction B atmosphere Spots, plages Vis. photometry/spectroscopy Chromosphere, TR, corona Radio X-rays Usual proxies for stellar B Caii H&K emission Coronal X-ray emission cyclic variations Rotation activity relation Growth + saturation Rossby number : Ro = P rot τ c Hall et al. (2007) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

20 Indirect measurements: stellar activity Interaction B atmosphere Spots, plages Vis. photometry/spectroscopy Chromosphere, TR, corona Radio X-rays Usual proxies for stellar B Caii H&K emission Coronal X-ray emission cyclic variations Rotation activity relation Growth + saturation Rossby number : Ro = P rot τ c Pizzolato et al. (2003) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

Direct measurements of B: unpolarised light Direct B photosph measurements Zeeman effect Measure magnetic flux : B Atomic lines Molecular lines Multi-component models Weakly sensitive to B

21 Direct measurements of B: unpolarised light Direct B photosph measurements Zeeman effect Measure magnetic flux : B Atomic lines Molecular lines Multi-component models Weakly sensitive to B orientation Partly degenerate Johns-Krull & Valenti (1996) Low to moderate v sin i GJ 729, FeH Wing-Ford band Reiners & Basri (2006) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

22 Direct measurements of B: unpolarised light Direct B photosph measurements Zeeman effect Measure magnetic flux : B Atomic lines Molecular lines Multi-component models Weakly sensitive to B orientation Partly degenerate Low to moderate v sin i Shulyak et al. (2015) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

23 Direct measurements of B: spectropolarimetry Zeeman-induced polarisation circ. pol.: longitudinal field lin. pol. : transverse field 1 st detection on another star than the Sun: Babcock (1947) Information on vector B Differential measurement / weakly affected by modelling error Requires high S/N ( 10 4 ) Multi-line techniques (LSD) Donati et al. (1997) Babcock (1947) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

24 Direct measurements of B: spectropolarimetry Zeeman-induced polarisation circ. pol.: longitudinal field lin. pol. : transverse field 1 st detection on another star than the Sun: Babcock (1947) Information on vector B Differential measurement / weakly affected by modelling error Requires high S/N ( 10 4 ) Multi-line techniques (LSD) Donati et al. (1997) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

25 Direct measurements of B: spectropolarimetry Sensitive to vector properties Partial cancellation Blind to small-scale field Interpretation/modelling Longitudinal/transverse field monitoring Dipolar model Zeeman-Doppler Imaging Semel (1989) Use full information Implementations Donati & Brown (1997) Hussain et al. (2000) Piskunov & Kochukhov (2002) Carroll et al. (2012) Folsom et al. submitted Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

26 Direct measurements of B: spectropolarimetry Sensitive to vector properties Partial cancellation Blind to small-scale field Interpretation/modelling Longitudinal/transverse field monitoring Dipolar model Zeeman-Doppler Imaging Semel (1989) Use full information Implementations Donati & Brown (1997) Hussain et al. (2000) Piskunov & Kochukhov (2002) Carroll et al. (2012) Folsom et al. submitted Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

27 Direct measurements of B: spectropolarimetry Sensitive to vector properties Partial cancellation Blind to small-scale field Interpretation/modelling Longitudinal/transverse field monitoring Dipolar model Zeeman-Doppler Imaging Semel (1989) Use full information Implementations Donati & Brown (1997) Hussain et al. (2000) Piskunov & Kochukhov (2002) Carroll et al. (2012) Folsom et al. submitted Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

28 Direct measurements of B: spectropolarimetry Sensitive to vector properties Partial cancellation Blind to small-scale field Interpretation/modelling Longitudinal/transverse field monitoring Dipolar model Zeeman-Doppler Imaging Semel (1989) Use full information Implementations Donati & Brown (1997) Hussain et al. (2000) Piskunov & Kochukhov (2002) Carroll et al. (2012) Folsom et al. submitted Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

29 ZDI: performances and limitations (1/2) Input numerical simulation Credit: T. Gastine MagIC code Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

30 ZDI: performances and limitations (1/2) ZDI reconstruction v sin i=40 km/s 20 spectra S/N=6,000 l max=20 Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

31 ZDI: performances and limitations (1/2) ZDI reconstruction v sin i=10 km/s 10 spectra S/N=6,000 l max=10 Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

32 ZDI: performances and limitations (1/2) Input numerical simulation Credit: T. Gastine MagIC code Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

33 ZDI: performances and limitations (1/2) ZDI reconstruction v sin i=40 km/s 20 spectra S/N=6,000 l max=20 Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

34 ZDI: performances and limitations (1/2) ZDI reconstruction v sin i=10 km/s 10 spectra S/N=6,000 l max=10 Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

35 ZDI: performances and limitations (2/2) Magnetic models assume No velocity field Homogeneous brightness How can we take them into account? Beeck et al. (2011) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

36 ZDI: performances and limitations (2/2) Magnetic models assume No velocity field Homogeneous brightness How can we take them into account? Credit: B. Beeck Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

37 ZDI: performances and limitations (2/2) Magnetic models assume No velocity field Homogeneous brightness How can we take them into account? Rosen &Kochukhov (2012) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

38 Outline 1 Magnetic fields: a crucial ingredient of stellar physics 2 Detection and characterization of stellar magnetic fields 3 A brief overview of M dwarfs magnetism Activity of M dwarfs Magnetic fields of M dwarfs in unpolarised light The first spectropolarimetric survey 4 Summary Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

39 Activity of M dwarfs Rotation activity relation Early-mid M dwarfs: similar G-K High Ro: anti-correlated Low Ro: plateau No break at FCL Late M dwarfs low activity at low Ro No L rad /L bol saturation Activity cycles Evidence for long-term variability Hints of cycles McLean et al. (2011) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

40 Activity of M dwarfs Rotation activity relation Early-mid M dwarfs: similar G-K High Ro: anti-correlated Low Ro: plateau No break at FCL Late M dwarfs low activity at low Ro No L rad /L bol saturation Activity cycles Evidence for long-term variability Hints of cycles Gomes da Silva et al. (2012) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

41 Magnetic fields of M dwarfs in unpolarised light Rotation Bf relation Early-mid M dwarfs: similar G-K High Ro: anti-correlated Low Ro: plateau No break at FCL Late M dwarfs low Bf at low Ro Reiners (2012) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

42 Spectropolarimetric survey: fully convective stars Fully convective boundary Sharp transition 0.5 M Magnetic topology Differential rotation Partial agreement with DNS Browning (2008) Morin et al. (2008a,b) Donati et al. (2008) Phan-Bao et al. (2009) Similar transition among TTS MaPP Large Program Gregory et al. (2012) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

43 Spectropolarimetric survey: fully convective stars Fully convective boundary Sharp transition 0.5 M Magnetic topology Differential rotation Partial agreement with DNS Browning (2008) Morin et al. (2008a,b) Donati et al. (2008) Phan-Bao et al. (2009) Coronal extrapolations by M. Jardine from surface magnetic fields reconstructed by Donati et al. (2008), Morin et al. (2008a) Similar transition among TTS MaPP Large Program Gregory et al. (2012) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

(2008) Phan-Bao et al. (2009) Coronal extrapolations by M. Jardine from surface magnetic fields reconstructed by Donati et al.

44 Spectropolarimetric survey: fully convective stars Fully convective boundary Sharp transition 0.5 M Magnetic topology Differential rotation Partial agreement with DNS Browning (2008) Morin et al. (2008a,b) Donati et al. (2008) Phan-Bao et al. (2009) Coronal extrapolations by M. Jardine from surface magnetic fields reconstructed by Donati et al. (2008), Morin et al. (2008a) Similar transition among TTS MaPP Large Program Gregory et al. (2012) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

45 Spectropolarimetric survey: very low mass stars VLM rapidly rotating stars 2 groups of stars 0.2 M Similar stellar params Radically magnetisms Morin et al. (2010) Explanation Variability / cycles? No switch in 3 yr Effect of age? Dynamo bistability? Morin et al. (2011) Gastine et al. (2013) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

46 Spectropolarimetric survey: very low mass stars VLM rapidly rotating stars 2 groups of stars 0.2 M Similar stellar params Radically magnetisms Morin et al. (2010) Explanation Variability / cycles? No switch in 3 yr Effect of age? Dynamo bistability? Morin et al. (2011) Gastine et al. (2013) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

47 Spectropolarimetric survey: very low mass stars VLM rapidly rotating stars 2 groups of stars 0.2 M Similar stellar params Radically magnetisms Morin et al. (2010) Explanation Variability / cycles? No switch in 3 yr Effect of age? Dynamo bistability? Morin et al. (2011) Gastine et al. (2013) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

48 Spectropolarimetric survey: latest developments Moderately active M dwarfs dipole-dominated Ro>1 similar to Sun-like Dipole-dominated 0.1<Ro<1 similar to more active FC Multipolar+toroidal 0.1<Ro<1 bistability? É. Hébrard et al. in prep. Reconciling Stokes I and V Numerical simulation Dipole-dominated LS field + small-scale structure B = 2.3 kg B V = 450 G Yadav et al. (2015) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

Spectropolarimetric survey: latest developments Moderately active M dwarfs dipole-dominated Ro>1 similar to Sun-like Dipole-dominated 0.1<Ro<1 similar to more active FC Multipolar+toroidal 0.

49 Spectropolarimetric survey: latest developments Moderately active M dwarfs dipole-dominated Ro>1 similar to Sun-like Dipole-dominated 0.1<Ro<1 similar to more active FC Multipolar+toroidal 0.1<Ro<1 bistability? É. Hébrard et al. in prep. Reconciling Stokes I and V Numerical simulation Dipole-dominated LS field + small-scale structure B = 2.3 kg B V = 450 G Yadav et al. (2015) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

50 Outline 1 Magnetic fields: a crucial ingredient of stellar physics 2 Detection and characterization of stellar magnetic fields 3 A brief overview of M dwarfs magnetism 4 Summary Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

51 Summary B crucial for CS FC vs PC stars M dwarfs and young Suns Spectropolarimetry: powerful tool Combined w/ unpolarised light, activity Magnetograms modelling Magnetospheres SPI RV signals Future: nir spectropolarimetry SPIRou CRIRES+ Adapted from Reiners (2008) star sketches credit J. Bennett et al. Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

52 Summary B crucial for CS FC vs PC stars M dwarfs and young Suns Spectropolarimetry: powerful tool Combined w/ unpolarised light, activity Magnetograms modelling Magnetospheres SPI RV signals Future: nir spectropolarimetry SPIRou Donati et al. (2008), Morin et al.(2008a,b, CRIRES+ 2010), Hébrard et al. in prep. Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

Summary B crucial for CS FC vs PC stars M dwarfs and young Suns Spectropolarimetry: powerful tool Combined w/ unpolarised light, activity Magnetograms modelling

53 Summary B crucial for CS FC vs PC stars M dwarfs and young Suns Spectropolarimetry: powerful tool Combined w/ unpolarised light, activity Magnetograms modelling Magnetospheres SPI RV signals Future: nir spectropolarimetry SPIRou CRIRES+ Vidotto et al. (2014) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

54 Summary B crucial for CS FC vs PC stars M dwarfs and young Suns Spectropolarimetry: powerful tool Combined w/ unpolarised light, activity Magnetograms modelling Magnetospheres SPI RV signals E. Hébrard et al. (2014) Future: nir spectropolarimetry SPIRou CRIRES+ Donati et al. (2014) Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

Magnetograms modelling Magnetospheres SPI RV signals Future: nir

55 Summary B crucial for CS FC vs PC stars M dwarfs and young Suns Spectropolarimetry: powerful tool Combined w/ unpolarised light, activity Magnetograms modelling Magnetospheres SPI RV signals Future: nir spectropolarimetry SPIRou CRIRES+ SPIRou Julien Morin Magnetometry of M dwarfs: methodology & results 02/11/ / 23

Does inertia determine the magnetic topology of low-mass stars?

Does inertia determine the magnetic topology of low-mass stars? Julien Morin Institut für Astrophysik Göttingen T. Gastine Max Planck Institut für Sonnensystemforschung A. Reiners Institut für Astrophysik