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Pulsations and magnetic activity in the IR

Pulsations and magnetic activity in the IR. Rafa Garrido & Pedro J. Amado Instituto de Astrofísica de Andalucía, CSIC. Granada. Acoustic oscillations. Angular dependence (l,m). Radial dependence (n). 1996 standard solar model. inclusion of He settling

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Pulsations and magnetic activity in the IR

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  1. Pulsations and magnetic activity in the IR Rafa Garrido & Pedro J. Amado Instituto de Astrofísica de Andalucía, CSIC. Granada

  2. Acoustic oscillations Angular dependence (l,m) Radial dependence (n)

  3. 1996 standard solar model inclusion of He settling & improved physics base of convection zone better physics for core needed Standard solar model

  4. Standard solar model Differential rotation

  5. Small and large separations Solar oscillations (VIRGO-SOHO)

  6. Asteroseismic diagram:J. C. Christensen-Daslgaard, Rev. Mod. Phys., 74, 1073

  7. d Scuti g Doradus Variability Zoo

  8. Giants  UMa  Hya GSC 09137- 03505  aBoo 

  9. LAST RESULTS WITH HARPSB. Mosser (Corot week 6: May 2004, Orsay) • A clear signature of the large separation : • Dn  89 mHz

  10. HARPS PERFORMANCE 2 minutes integration time for V=6 on the ESO 3.6m: σv=1 ms-1@ vsini= 0 kms-1 σv=3 ms-1@ vsini=10 kms-1

  11. Benefits from the IR Flux gain

  12. Benefits from the IR magnetic sensitivity

  13. Problems • Theory • mode selection (amplitudes) • amplitude & phase changes • input physics in models • convection & overshooting • diffusion & settling • rotation • magnetic field • Observations • mode identification (spectroscopy & photometry) • data analysis

  14. Active stars:Science goals • Dynamo geometry • Solar-like or something different? • Polar spots and active belts • Spot structure • Resolved or not? • Differential rotation and meridional flows • Lifetimes of individual spots and active regions • Stellar “butterfly diagrams” • Different stellar types • Pre-main sequence stars • Young main-sequence stars with[out] radiative interiors • Subgiants and giants

  15. A A Intensity Intensity -v sin i v(spot) v sin i -v sin i v(spot) v sin i Doppler Imaging

  16. Data requirements • Time-series of hi-res (R > 30000) spectra: • Good supply of unblended intermediate-strength lines (!) • Broad-band light-curves. • TiO and other temperature diagnostics.

  17. Least-Square Deconvolution • Assume observed spectrum = mean profile convolved with depth-weighted line pattern: • De-convolve mean profile zkvia least squares: • S/N improves from ~100 to ~2500 per 3 km s–1 pixel with ~2500 lines. Depth-weighted line pattern,  - KNOWN  Mean profile, z (UNKNOWN) Rotationally broadened spectrum, r – KNOWN =

  18. DI Maps AB Dor

  19. DI Maps VW Cep

  20. ZDI Maps AB Dor

  21. Benefits from the IR • Spectral lines are less blended in the infrared. Hence, line profile variations are more clearly detected • The Zeeman effect is enhanced for lines in the IR • Radiation flux and pulsation amplitudes increase with increasing wavelength for cooler stars. • IR lines can probe different parts of the atmosphere.

  22. Benefits from the IR • Sun continuum contrast between photosphere and Tspot =4250 K: • ≈ 20% @ 0.6 µm • ≈ 70% @ 2.2 µm • Resolving the telluric absorption lines (intrinsically narrow ~5 km s−1) Pontoppidan & van Dishoeck, 2004, astroph 0405629 • Zeeman sensitivity: the Fe I line at 1.56 µm splits by twice the FWHM in 1.5 kG fields (slowly rotating stars): 2-3 times more sensitive than optical lines (Giampapa PASP 109)

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