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Asteroseismology of solar-type stars Revolutionizing the study of solar-type stars

Asteroseismology of solar-type stars Revolutionizing the study of solar-type stars Hans Kjeldsen, Aarhus University. Asteroseismology: Solar-like stars. CoRoT HD 49385. Measuring oscillation frequencies Identify modes (p, g, mixed, l, n, m) Compute model frequencies

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Asteroseismology of solar-type stars Revolutionizing the study of solar-type stars

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  1. Asteroseismology of solar-type stars Revolutionizing the study of solar-type stars Hans Kjeldsen, Aarhus University

  2. Asteroseismology: Solar-like stars CoRoT HD 49385 • Measuring oscillation frequencies • Identify modes (p, g, mixed, l, n, m) • Compute model frequencies • Compare observed frequencies with the model The Sun Christensen-Dalsgaard et al. 1995

  3. Observations: Challenges • Accuracy of oscillation frequencies • Mode identification, avoided crossings, (curvature in the Echelle diagram) • Rotational splitting, mode lifetime, mode amplitudes, granulation

  4. Helioseismology  asteroseismology

  5. State-of-the-art Ground-based asteroseismology of solar-type stars UCLES at the AAT UVES at the VLT HARPS at ESO 3.6m

  6. Ground-based • In most cases: • Low SNR • Short obs. period

  7. (Fabien Carrier)

  8. (Fabien Carrier)

  9. High signal-to-noise observations of solar-like oscillations

  10. Mixed mode

  11. Martic et al. 2004: amp = 40 cm/s per mode = 6-7 ppm per mode

  12. Brown et al.1991 Martic et al. 2004: amp = 40 cm/s per mode = 6-7 ppm per mode

  13. 0 3 1 • ??? • 3 1 2 0

  14. Velocities ofa Cen A with UVES/VLT Precision: 50-70 cm/s. Cadence 26 seconds!

  15. 35 UVES/VLT2 + UCLES/AAT Butler, Bedding, Kjeldsen et al. 2003, 2004

  16. 2 0 3 1

  17. Radial p-mode (radial orders)

  18. α Centauri system OPAL EOS, OPAL96 opacity, He, Z settling (Teixeira et al.)

  19. α Centauri A

  20. α Centauri A

  21. α Centauri B

  22. α Centauri B

  23. Models: Challenges • Input physics • Properties: rotation, mixing • Surface frequency offset • Avoided crossings – sensitivity to finer details in the models

  24. The Surface Offset O - C

  25. BiSON Model S

  26. The Surface Offset MODEL S GOLF radial order, n 1. Frequency (f) 3038.95 3034.15 17-25 (21) 2. Large separation 135.855 134.810 17-25 (21) 3. f(n=17) 2497.35 2496.04 17 4. f(n=13) 1957.46 1957.45 13 0.16 % 0.78 % 0.05 % 0.0005 %

  27. Observations: Challenges • Accuracy of oscillation frequencies • Mode identification, avoided crossings, (curvature in the Echelle diagram) • Rotational splitting, mode lifetime, mode amplitudes, granulation

  28. How do we improve this?

  29. How do we improve this? • Higher frequency resolution

  30. How do we improve this? • Higher frequency resolution Space missions

  31. How do we improve this? • Higher frequency resolution • Lower noise

  32. Granulation dominated Oscillations dominated

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