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Stellar oscillations across the H-R diagram

Stellar oscillations across the H-R diagram. Helioseismology. Larger.  Surface spatial scale . Smaller. Shallower. Millions of independent oscillation frequencies excited simultaneously Each mode samples the interior in a different and complementary way

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Stellar oscillations across the H-R diagram

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  1. Stellar oscillations across the H-R diagram

  2. Helioseismology Larger  Surface spatial scale  Smaller Shallower • Millions of independent oscillation frequencies excited simultaneously • Each mode samples the interior in a different and complementary way • This provides a detailed calibration of the physics of standard solar models  Interior sampled  Deeper

  3. Calibrating solar physics Dziembowski et al. (1992) • New radiative opacities significantly improved standard solar models • Models with settling of heavy elements agreed even more closely • Remaining discrepancies in the outer layers were resolved by a new EOS Bahcall et al. (1997)

  4. Asteroseismology • New opportunities to probe the fundamental physics of the models • Understanding the solar evolution in a broader context from stellar ages • Only the lowest degree modes are detectable in distant stars (l< 3) Bedding & Kjeldsen (2003)

  5. Observing techniques Light variation Appourchaux et al. (2008) Velocity variation Bouchy et al. (2004)

  6. Solar-like oscillations

  7. Mission: SOHO • SOlar and Heliospheric Observatory, launched in December 1995 • Sun-as-a-star data from VIRGO experiment, SPM and LOI instruments • 5.5-cm aperture, silicon photodiode detectors

  8. Stellar density and age Elsworth & Thompson (2004) • Large frequency spacing <Dn> scales with average density of the star • Small frequency spacing <dn> sensitive to interior gradients, proxy for age • Probe evolution of activity and rotation as a function of stellar mass and radius Christensen-Dalsgaard (2004)

  9. Mission: WIRE • Wide-field InfraRed Explorer, launched in March 1999 • Primary instrument failed shortly after launch due to complete loss of coolant • 5.2-cm “star tracker” with CCD camera mounted to side of main instrument

  10. Radial differential rotation Fletcher et al. (2006) • WIRE 50-day time series of a Cen A has resolved the rotational splitting • Splitting as a function of radial order can indirectly probe differential rotation • Even low-degree modes allow rough inversions of the inner 30% of radius Gough & Kosovichev (1993)

  11. Mission: MOST • Microvariability and Oscillations of STars, launched in June 2003 • 15-cm primary mirror, two CCD cameras with Fabry lens array for stability • Up to two months per target, 100% duty cycle, few ppm photometry

  12. Surface differential rotation • Three seasons of precise MOST photometry for the solar-type star k1 Ceti • Latitudinal differential rotation pattern has same functional form as Sun • Kepler will obtain similar rotation measurements for 105 solar-type stars Ca HK period Walker et al. (2007)

  13. Mission: CoRoT • French-led ESA mission, successfully launched in December 2006 • 28-cm primary mirror, two science CCDs for planet transits and seismology • Interleaved 1-month and 5-month runs for 2.5 yrs, 100% duty cycle

  14. Convection zone depth • Expected seismic signal from a CoRoT 5-month observation of HD 49933 • Second differences (d2n) measure deviations from even frequency spacing • Base of the convection zone and He ionization create oscillatory signals Baglin et al. (2006)

  15. Mission: Kepler • NASA mission currently scheduled for launch in March 2009 • 105 square degrees just above galactic plane in the constellation Cygnus • Single field for 4-6 years, 100,000 stars 30 minute sampling, 512 at 1 minute

  16. Salabert et al. (2004) Oscillations and magnetic cycles • Solar p-mode shifts first detected in 1990, depend on frequency and degree • Even the lowest degree solar p-modes are shifted by the magnetic cycle • Unique constraints on the mechanism could come from asteroseismology Libbrecht & Woodard (1990)

  17. Cycle-induced frequency shifts • Solar p-mode shifts show spread with degree and frequency dependence • Normalizing shifts by our parametrization removes most of the dependencies • Kepler will document similar shifts in hundreds of solar-type stars Metcalfe et al. (2007)

  18. Toutain & Frohlich (1992) Red supergiants Kiss et al. (2006)

  19. (p-)ressure and (g-)ravity Montgomery & Winget (1999)

  20. Excitation mechanisms Dutch Open Telescope

  21. Handler (2005) Intermediate-mass pulsators

  22. d Scuti stars Breger et al. (2005)

  23. g Dor stars Rowe et al. (2007)

  24. roAp stars Kurtz et al. (2002, 2005)

  25. Pamyatnykh (1999) Massive pulsators

  26. SPB stars Aerts et al. (2006)

  27. b Cep stars Aerts et al. (2006)

  28. Fontaine et al. (2007) Subdwarf variables

  29. sdB stars Fontaine et al. (2007) Schuh et al. (2006)

  30. Corsico & Althaus (2006) White dwarf variables

  31. DOV stars Winget et al. (1991)

  32. Winget et al. (2004) DBV stars Sullivan et al. (2008)

  33. DAV stars Kanaan et al. (2005)

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