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A Practical Introduction to Stellar Nonradial Oscillations (i)

Rich Townsend University of Delaware. A Practical Introduction to Stellar Nonradial Oscillations (i). ESO Chile ̶ November 2006. TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A A A A. Overview. Historical Perspective Radial pulsators

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A Practical Introduction to Stellar Nonradial Oscillations (i)

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  1. Rich Townsend University of Delaware A Practical Introduction to Stellar Nonradial Oscillations (i) ESO Chile ̶ November 2006 TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAA

  2. Overview • Historical Perspective • Radial pulsators • Nonradial pulsators • Waves in stars • Global oscillations • Surface variations • Rotation effects • Driving mechanisms

  3. p-mode Surface Variations

  4. g-mode Surface Variations

  5. p modes vs. g modes

  6. Carnot Cycle

  7. Excitation Mechanisms • Add heat when temperature is high • Remove heat when temperature is low • Mechanisms: • κ : opacity • ε : nuclear energy • δ : superadiabatic stratification • γ : ionization

  8. OPAL / OP Opacities

  9. 5 M¯ model

  10. WN model

  11. Brown Dwarf model

  12. Asteroseismology • Compare observations against models • Frequencies • Multi-color light curve • Amplitudes • Phases • Spectroscopy • Line-profile variations • Mean profiles

  13. Frequencies

  14. ℓ = 1 ℓ = 2 ℓ = 3 Photometric Amplitudes

  15. Line-Profile Variations

  16. lpv: Time-Series

  17. Modeling • Photometric • Semi-analytical • Spectroscopic • Semi-analytical • Moments • TVS • Numerical • BRUCE/KYLIE • PULSTAR

  18. Photometric Modeling • Stamford & Watson (1981) • Semi-analytical formula for flux changes

  19. Photometry of SPB stars

  20. Spectroscopic Modeling • Represent stellar surface with mesh • Perturb mesh with pulsation(s) • Rasterize mesh • Synthesize spectra for each pixel • Combine spectra

  21. Spectral Synthesis • For each pixel: • Teff • log g • V •  • Interpolate spectrum in intensity grid

  22. Pulsation & Rotation • Coriolis force becomes significant when Ω/ω > 0.5 • Pulsation confined within equatorial waveguide • New formula • Townsend (2003) • Extends Dziembowski (1977) • Low-frequency (SPBs)

  23. Townsend (2003) Effects of Rotation

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