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The Herbig Ae/Be stars: what we have learnt with ESPaDOnS

The Herbig Ae/Be stars: what we have learnt with ESPaDOnS. E. Alecian, G.A. Wade, C. Catala, C. Folsom, J. Grunhut, J.-F. Donati, P. Petit, S. Bagnulo, S.C. Marsden, J.D. Landstreet, T. Böhm, J.-C. Bouret, J. Silvester. Armagh Workshop 21/02/2008. Problematic 1.

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The Herbig Ae/Be stars: what we have learnt with ESPaDOnS

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  1. The Herbig Ae/Be stars: what we have learnt with ESPaDOnS E. Alecian, G.A. Wade, C. Catala, C. Folsom, J. Grunhut, J.-F. Donati, P. Petit, S. Bagnulo, S.C. Marsden, J.D. Landstreet, T. Böhm, J.-C. Bouret, J. Silvester Armagh Workshop 21/02/2008

  2. Problematic 1 • Origin of the magnetic fields in the Ap/Bp stars • Favoured hypothesis : the fossil field hypothesis • some of the intermediate mass PMS star should be magnetic • topology of B(PMS A/B) = topology B(Ap/Bp) • intensity B(PMS A/B) compatible with intensity B(Ap/Bp) (assuming the magnetic flux conservation) • Other hypothesis : the core dynamo Armagh Workshop 21/02/2008

  3. Problematic 2 • Origin of the slow rotation of the Ap/Bp stars • Hypothesis 1 : magnetic braking during the PMS phase(Stepien & Lanstreet 2002) • magnetic PMS A/B stars should exist • PMS A/B stars should have a disk • Evolution of the rotation during the PMS phase • Hypothesis 2 : the magnetic field cannot survive in fast rotators (Lignières et al. 1996) • No magnetic fast rotators during the PMS phase Armagh Workshop 21/02/2008

  4. Strategy (1) • Observation of the field Herbig Ae/Be stars • Detection of magnetic field • Characterisation of their magnetic fields • Compare to the magnetic fields of Ap/Bp stars • Fossil field hypothesis test • vsini determination • Compare to vsini of Ap/Bp star • vsini as a function of age • Origin of slow rotation hypothesis tests Armagh Workshop 21/02/2008

  5. Strategy (2) • Observations of the Herbig stars in young clusters and associations • stars of a single cluster: = age and = initial conditions • ≠ clusters ≠ ages and ≠initial conditions • Disentangle evolutionary effects from initial condition effects • Understand the evolution of the magnetic field during the PMS phase, and its impact on the evolution of the stars Armagh Workshop 21/02/2008

  6. The Herbig Ae/Be stars } • A and B stars with emission lines • IR emission • Association with nebulae • Intermediate-mass PMS stars • Progenitors of the main sequence A/B stars • Characteristics associated with magnetic activity : • resonance lines as N V and O VI, X-ray emission :  hot chromospheres or coronae (e.g. Bouret et al. 1997) • magnetospheric accretion(e.g. Mannings & Sargent 1997) • rotational modulation of resonance lines :  wind structured by magnetic field (e.g. Catala et al. 1989, 1999) definition (Herbig 1960) Armagh Workshop 21/02/2008

  7. Magnetic fields in Herbig Ae/Be stars ? • AB Aur : Catala et al. (1993), Catala et al. (1999) • no detection • HD 100546 : Donati et al. (1997) • no detection • HD 104237 : Donati et al. (1997) • 1st detection (recently confirmed) • HD 139614 : Hubrig et al. (2004) • detection not confirmed with more accurate observations • HD 101412 : Wade et al. (2007) • detection (recently confirmed) But now we have ESPaDOnS ! Armagh Workshop 21/02/2008

  8. ESPaDOnS (CFHT, Hawaii) • High-resolution spectropolarimeter : R = 65000, broad spectral range (370 - 1080 nm) • Reduction : Libre-Esprit package (Donati et al. 1997, 2007) • Least Squares Deconvolution method (Donati et al., 1997) • More lines, better S/N ratio, larger magnitude V range of the star • Increase our chances to detect magnetic fields Armagh Workshop 21/02/2008

  9. Field Herbig Ae/Be stars (HAeBe) study Armagh Workshop 21/02/2008

  10. Our sample birthlines Palla & Stahler (1993) • Catalogues : Vieira et al . (2003) and Thé et al. (1994) • 55 Herbig Ae/Be stars • 1.5 – 15 Msun • PMS life = from birthline to ZAMS ZAMS  Armagh Workshop 21/02/2008

  11. Our sample Convective envelope disappearing • Catalogues : Vieira et al . (2003) and Thé et al. (1994) • 55 Herbig Ae/Be stars • 1.5 – 15 Msun • PMS life = from birthline to ZAMS • Stars: • with convective envelope, or • with convective core, or • totally radiative Convective core apparition  Armagh Workshop 21/02/2008

  12. Observations and reduction • For each star: • (one or many) Stokes I and V spectra • Determination of Teff and log(g) • LSD method: mask of Teff and log(g) of the star, not including Balmer lines and lines contaminated by emission • Searching for a Zeeman signature in the LSD V profile Armagh Workshop 21/02/2008

  13. Wonderful Zeeman signatures !!! Results B3, vsini~26 km/s B9, vsini~41 km/s 55 observed, 4 magnetic  ~7% magnetic Herbig Ae/Be stars A0, vsini~8.6 km/s A2, vsini~9.8 km/s Armagh Workshop 21/02/2008

  14. HD 200775 • Binary SB2 (P~3.9 y) Alecian et al. (2008) Armagh Workshop 21/02/2008

  15. HD 200775 • Binary SB2 (P~3.9 y) Alecian et al. (2008) Armagh Workshop 21/02/2008

  16. HD 200775 • Binary SB2 (P~3.9 y) • TB~TA=19000 K • Primary magnetic, vsini~26 km/s • Secondary non-magnetic, vsini~56 km/s • Emission from the secondary • Secondary largely redder than the primary  Ls>Lp and Ms>Mp Alecian et al. (2008) Armagh Workshop 21/02/2008

  17. HD 72106 • Binary SB2 • asini = 0.8 " • Porb>1600 d • Primary: B9 Ap ZAMS, magnetic, vsini~41 km/s • Secondary: A3 PMS, non-magnetic, vsini~54 km/s Folsom et al., in prep. Armagh Workshop 21/02/2008

  18. HD 72106 P S Armagh Workshop 21/02/2008 Folsom et al., in prep.

  19. HD 72106 • Binary SB2 • asini = 0.8 " • Porb>1600 d • Primary: B9 Ap ZAMS, magnetic, vsini~41 km/s • Secondary: A3 PMS, non-magnetic, vsini~54 km/s Folsom et al., in prep. Armagh Workshop 21/02/2008

  20. HD 190073 • Single, PMS • Te = 9250K, vsini=0-8.3 km/s • Numerous emission in the spectrum: fwhm = 65 km/s Catala et al. (2007) Armagh Workshop 21/02/2008

  21. HD 190073 Catala et al. (2007) Armagh Workshop 21/02/2008

  22. HD 190073 • Single, PMS • Te = 9250, vsini=0-8.3 km/s • Numerous emission in the spectrum: fwhm = 65 km/s • Halpha: Pcygni dM/dt = 1.4 10-8 M/y v = 290 km/s Tbase = 18000 K Catala et al. (2007) Armagh Workshop 21/02/2008

  23. V380 Ori Armagh Workshop 21/02/2008

  24. V380 Ori Armagh Workshop 21/02/2008

  25. V380 Ori Tp = 10500 K Ts = 6000 K Armagh Workshop 21/02/2008

  26. V380 Ori Armagh Workshop 21/02/2008

  27. V380 Ori • Binary SB2 • Primary: B9 magnetic • Secondary: G0.5 non-magnetic • LSD profiles Armagh Workshop 21/02/2008

  28. V380 Ori LSD Profiles Primary Secondary vsiniP~10 km/s vsiniS~20 km/s Armagh Workshop 21/02/2008

  29. Magnetic field characterisation : Method • Observations of the stars at different rotation phase • Compute I and V: • I(,) : G(instr,v(,) ) • V(,) dI/dBl(,) (weak field approximation) • Bl(,) : oblique rotator model (Stift 1975) • Integration over the surface : limb-darkening law • Comparison of the synthetic to observed I, V and Bl • Compute 2 for (P,0,,Bd,ddip) • 2 minimisation  B  D Obs ddip i Armagh Workshop 21/02/2008

  30. Magnetic field characterisation : HD 200775 P = 4.328 d. i = 13 °  = -102° Bd = 1000 G ddip = 0.10 R* On the ZAMS: P = 1.2 d Bd = 3.6 kG Alecian et al. (2008) Armagh Workshop 21/02/2008

  31. Magnetic field characterisation : HD72106 P = 0.63995 d. i = 23°  = 60° Bd = 1300 G ddip = 0 R* On the ZAMS: P = 0.63995 d Bd = 1.3 kG Folsom et al., in prep. Armagh Workshop 21/02/2008

  32. Magnetic field characterisation : HD 190073 Catala et al. (2007) • 3 different hypothesis : • Pole-on star •  = 0 • Long Period • In all cases: • Simple dipolar Zeeman signature • Signature stable over more than 2 years strong probability for an organised magnetic field • Bd = 100 - 1000 G ZAMS: Bd = 400 - 4000 G Armagh Workshop 21/02/2008

  33. Magnetic field characterisation : V380 Ori • P = 7.6 d. • i = 34° • = -95° Bd = 1.4 kG ddip = 0 R* ZAMS P=4.5 d Bd=2.4kG 2 dipole solutions • P = 9.8 d. • i = 47° • = -95° Bd = 1.4 kG ddip = 0 R* ZAMS P=5.8 d Bd=2.4kG Armagh Workshop 21/02/2008

  34. Other detections HD 104237 HD 101412 • SemelPol +UCLES (AAT) = antecedent of ESPaDOnS • Simple Zeeman signature consistent with an organised field A4, vsini = 11.6 km/s Bl = -50 G A0, vsini = 4.8 km/s Bl = -120 G Armagh Workshop 21/02/2008 Thanks to S.C. Marsden

  35. First conclusions • 7% magnetic HAeBe stars • Projection of magnetic Ap/Bp stars on the PMS phase  prediction of 5-10% magnetic HAeBe stars • Large scale organised magnetic field • Magnetic intensity of the HAeBe projected on the ZAMS : same order of the intensity of B(Ap/Bp): (assuming the magnetic flux conservation) • HD 200775: on the ZAMS Bd = 3.6 kG • V380 Ori: on the ZAMS Bd = 2.4 kG • HD 72106: already on the ZAMS Bd = 1.3 kG • HD 190073: on the ZAMS Bd = 400 - 4000 G Strong arguments in favour of the fossil field theory Armagh Workshop 21/02/2008

  36. Statistical Study

  37. The undetected sample • 41 stars • Detection significance distribution • Monte-Carlo simulation: • i: random distribution • : bimodal distribution (0° or 90°) • random phase for each data • dipole of fixed B Wade et al., in prep. Armagh Workshop 21/02/2008

  38. The undetected sample • 41 stars • Detection significance distribution • Monte-Carlo simulation: • i: random distribution • : bimodal distribution (0° or 90°) • random phase for each data • dipole of fixed B Wade et al., in prep. Armagh Workshop 21/02/2008

  39. The undetected sample • 41 stars • Detection significance distribution • Monte-Carlo simulation: • i: random distribution • : bimodal distribution (0° or 90°) • random phase for each data • dipole of fixed B Wade et al., in prep. Armagh Workshop 21/02/2008

  40. The undetected sample • 41 stars • Detection significance distribution • Monte-Carlo simulation: • i: random distribution • : bimodal distribution (0° or 90°) • random phase for each data • dipole of fixed B • Kolmogorov-Smirnov test Homogeneous population of dipole with B<450 G Wade et al., in prep. Armagh Workshop 21/02/2008

  41. Distribution of vsini Magnetic HAeBe stars Non magnetic HAeBe stars • All field magnetic HAeBe are slow rotators • No magnetic HAeBe are fast rotators • Magnetic HAeBe stars seem to have been braked more than the non-magnetic HAeBe stars Armagh Workshop 21/02/2008

  42. Period in function of time • No clear evolution of the period • Majority of HAeBe: between 40 and 80% of their PMS track • To study period evolution we need younger stars than our sample Armagh Workshop 21/02/2008

  43. Evolution of vsini to the ZAMS Normal HAeBe on the ZAMS Normal A/B stars Normal HAeBe Royer et al. (2007) • vsini HAeBe on the ZAMS close to normal A/B stars • Evolution from HAeBe age to MS consistent with angular momentum conservation Armagh Workshop 21/02/2008

  44. Cluster study Armagh Workshop 21/02/2008

  45. NGC 6611 sample • Age = ~1 Myr • Younger than HAeBe • 3 - 20 Msun • Fill the hole in the HRD  Armagh Workshop 21/02/2008

  46. NGC 2244 Sample • Age ~ 8 Myr • 2 - 20 Msun Armagh Workshop 21/02/2008

  47. NGC 2264 sample • Age = 9Myr • 1.5 - 9 Msun Armagh Workshop 21/02/2008

  48. Cluster results NGC6611 W601 NGC 2264 83 NGC2244 201 B1.5, vsini~180 km/s B3, vsini~65 km/s B1, vsini~25 km/s 17 observed stars 1 magnetic 17 observed stars 1 magnetic 29 observed stars 1 magnetic Alecian et al. (2008), accepted Armagh Workshop 21/02/2008

  49. vsini of the cluster magnetic stars vsini age Sp.T. • NGC6611 W601 180 km/s ~ 1 Myr B1.5 • NGC2244 201 25 km/s ~ 8 Myr B1 • Can we see a sign of the evolution of the rotation in the magnetic HAeBe stars? Alecian et al. (2008), accepted Armagh Workshop 21/02/2008

  50. Conclusions (1) : Field HAeBe study • Magnetism: • 7% magnetic HAeBe • HAeBe magnetism in favour of the fossil field hypothesis • Rotation: • vsini(magnetic HAeBe) < vsini(non magnetic HAeBe) • Magnetic HAeBe: slow rotators and very young • A braking mechanism acts very early during the PMS phase • Dvsini(HAeBe on ZAMS) = Dvsini(A/B Norm) • Constant angular momentum evolution from the age of HAeBe to the MS Armagh Workshop 21/02/2008

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