Seismology of the Sun and solar-like stars - PowerPoint PPT Presentation

seismology of the sun and solar like stars n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Seismology of the Sun and solar-like stars PowerPoint Presentation
Download Presentation
Seismology of the Sun and solar-like stars

play fullscreen
1 / 60
Seismology of the Sun and solar-like stars
78 Views
Download Presentation
catrin
Download Presentation

Seismology of the Sun and solar-like stars

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Seismology of the Sun and solar-like stars Jørgen Christensen-Dalsgaard Institut for Fysik og Astronomi, Aarhus Universitet

  2. M. J. Thompson R. Howe J. Schou S. Basu R. M. Larsen J. M. Jensen Hans Kjeldsen Teresa Teixeira Tim Bedding Maria Pia Di Mauro Andrea Miglio Collaborators

  3. Where it all started Grec et al., Nature 288, 541; 1980

  4. Basic properties of oscillations • Behave like spherical harmonics: Plm(cos ) cos(m  -  t) • kh = 2  / h = [l(l+1)]1/2/r

  5. Hence Lower turning point rt where kr = 0: Asymptotics of frequencies Acoustic-wave dispersion relation

  6. Rays

  7. Inversion with rays

  8. Observing a Doppler image

  9. VIRGO on SOHO (whole-disk): Data on solar oscillations Observations: MDI on SOHO

  10. Observed frequencies m-averaged frequencies from MDI instrument on SOHO 1000 s error bars

  11. A reference solar model • Model S: • OPAL96 equation of state • OPAL 92 opacities • Nuclear parameters from Bahcall & Pinsonneault (1994) • Diffusion and settling of helium and heavy elements from Michaud & Proffitt (1993) • Mixing-length theory of convection

  12. Frequency differences, Sun - model

  13. No settling No settling Including settling The solar internal sound speed Sun - model

  14. The solar internal sound speed Sun - model

  15. Settling Nuclear burning Changes in composition • The evolution of stars is controlled by the changes in their interior composition: • Nuclear reactions • Convective mixing • Molecular diffusion and settling • Circulation and other mixing processes outside convection zones

  16. Including relativistic effects No relativistic effects Relativistic electrons in the Sun Elliot & Kosovichev (1998; ApJ 500, L199)

  17. Pijpers, Houdek et al. Z = 0.015 Model S Revision of solar surface abundances Asplund et al. (2004; A&A 417, 751): • Improvements: • Non-LTE analysis • 3D atmosphere models • Consistent abundance determinations for a variety of indicators

  18. How do we correct the models? Basu & Antia (2004; ApJ 606 L85): an opacity increase to compensate for lower Z is required Seaton & Badnell (submitted): recent Opacity Project results do indicate such an increase over the OPAL values.

  19. Rotational splitting

  20. Kernels for rotational splitting

  21. Base of convection zone Tachocline Near solid-body rotation of interior Inferred solar internal rotation

  22. Rotation of the solar interior BiSON and LOWL data; Chaplin et al. (1999; MNRAS 308, 405)

  23. Tachocline oscillations ● GONG-RLS ▲MDI-RLS ∆ MDI-OLA See Howe et al. (2000; Science 287, 2456)

  24. Zonal flows Rotation rate - average value at solar minimum Vorontsov et al. (2002; Science 296, 101)

  25. Radial development of zonal flows Howe et al., in preparation

  26. Observed and modelled dynamics Non-linear mean-field solar dynamo models Covas, Tavakol andMoss 6 1/2 year MDI inversion, enforcing 11-yr periodicity Vorontsov et al.

  27. Local helioseismology Tomography of three-dimensional, time-dependent properties of solar interior • Time-distance helioseismology • Ring-diagram analysis • Helioseismic holography

  28. Rays for local helioseismology Kosovichev et al. (2000; Solar Phys. 192, 159)

  29. Near-surface flows Meridional component Zonal component Time-distance analysis; Beck et al. (2002; ApJ 575, L47)

  30. 16:00 11 Jan 98 00:00 12 Jan 98 08:00 12 Jan 98 Emerging active region Kosovichev et al. (2000; Solar Phys. 192, 159

  31. Far-side imaging Lindsey & Braun (2000; Science 287, 1799)

  32. Far-side monitoring MDI on SOHO

  33. From the Sun to the stars

  34. What we expect:the solar case Grec et al., Nature 288, 541; 1980

  35. Asymptotics of p modes Large frequency separation:

  36. Small frequency separations Frequency separations:

  37. Asteroseismic HR diagram

  38. The present situation Bedding & Kjeldsen (2003)

  39. α Centauri A

  40. α Centauri A Observations with UVES on VLT (Butler et al, 2004; ApJ 600, L75)

  41. α Centauri A (Butler et al, 2004; ApJ 600, L75)

  42. α Centauri A VLT(UVES) and AAT(UCLES) optimally combined Bedding et al., ApJ, in press (astro-ph/0406471 )

  43. α Centauri B UVES (VLT) and UCLES (AAT) Kjeldsen et al. (in preparation)

  44. Classical variables (a) Pourbaix et al. (2002) (b) Pijpers (2003) (c) Kervella et al. (2003)

  45. Fitting the α Cen system Observable quantities for the system Model parameters: Fit using Marquardt method, with centred differences, using an 8-processor Linux cluster, implemented by T. C. Teixeira Choice of oscillation variables, from Bedding et al. fits to Butler et al. observations:

  46. α Centauri system MA: 1.11111 M¯ MB: 0.92828 M¯ X0: 0.71045 Z0: 0.02870 Age: 6.9848 Gyr OPAL EOS, OPAL96 opacity, He, Z settling (Teixeira et al.)

  47. : A : B α Centauri system

  48. α Centauri A Observations: use Bedding et al. fits Models: surf = 0.75

  49. α Centauri B Observations: use Bedding et al. fits Models: surf = 0.75

  50. α Centauri A Observations: use Bedding et al. fits Models: surf = 0.75