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Pulsations and magnetic activity Pulsations and magnetic activity in the IRin the IR
Rafa Garrido & Pedro J. AmadoRafa Garrido & Pedro J. Amado
Instituto de Astrofísica de Andalucía, CSIC. Instituto de Astrofísica de Andalucía, CSIC. GranadaGranada
tωie),(θY(r)f)t,θ,r,( n,lml
n,l,m
nlmp
p
Radial dependence (n)
Angular dependence (l,m)
Acoustic oscillations
Standard solar modelStandard solar model1996 standard solar model
inclusion of He settling& improved physics
base of convection zone
better physics for core needed
Small and large separationsSmall and large separationsSolar oscillations (VIRGO-SOHO)Solar oscillations (VIRGO-SOHO)
LAST RESULTS WITH HARPSLAST RESULTS WITH HARPSB. Mosser (Corot week 6: May 2004, Orsay)B. Mosser (Corot week 6: May 2004, Orsay)
• A clear signature of the large separation :
89 Hz
HARPS PERFORMANCEHARPS 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
5.15.05.0RV
RS
ProblemsProblems TheoryTheory
mode selection (amplitudes)mode selection (amplitudes) amplitude & phase changesamplitude & phase changes input physics in modelsinput physics in models
convection & overshootingconvection & overshooting diffusion & settlingdiffusion & settling rotationrotation magnetic fieldmagnetic field
ObservationsObservations mode identification (spectroscopy & photometry)mode identification (spectroscopy & photometry) data analysisdata analysis
Active stars:Active stars:Science goalsScience goals
Dynamo geometryDynamo geometrySolar-like or something different?Solar-like or something different?Polar spots and active beltsPolar spots and active belts
Spot structureSpot structureResolved or not?Resolved or not?
Differential rotation and meridional flowsDifferential rotation and meridional flowsLifetimes of individual spots and active regions Lifetimes of individual spots and active regions Stellar “butterfly diagrams”Stellar “butterfly diagrams”Different stellar typesDifferent stellar types
Pre-main sequence starsPre-main sequence starsYoung main-sequence stars with[out] radiative Young main-sequence stars with[out] radiative
interiorsinteriorsSubgiants and giantsSubgiants and giants
Intensity
A A
Intensity
v sin i-v sin i v(spot) v sin i-v sin i v(spot)
Doppler ImagingDoppler Imaging
Data requirementsData requirements Time-series of hi-res (R > 30000) spectra:Time-series of hi-res (R > 30000) spectra:
Good supply of unblended intermediate-strength lines (!)Good supply of unblended intermediate-strength lines (!) Broad-band light-curves.Broad-band light-curves. TiO and other temperature diagnostics.TiO and other temperature diagnostics.
Least-Square DeconvolutionLeast-Square Deconvolution Assume observed spectrum = Assume observed spectrum = mean profile mean profile convolved with convolved with
depth-weighted line pattern:depth-weighted line pattern:
De-convolve De-convolve mean profile zmean profile zkk via least squares:via least squares:
S/N improves from ~100 to ~2500 per 3 km sS/N improves from ~100 to ~2500 per 3 km s–1 –1 pixel with pixel with ~2500 lines. ~2500 lines.
=
Mean profile, z
(UNKNOWN)
Depth-weighted line pattern, - KNOWN
Rotationally broadened spectrum, r – KNOWN
2
22
2
where,0:Solve
j j
kjkj
k
zr
z
Benefits from the IRBenefits from the IR
Spectral lines are less blended in the infrared. Hence, Spectral lines are less blended in the infrared. Hence, line profile variations are more clearly detectedline profile variations are more clearly detected
The Zeeman effect is enhanced for lines in the IRThe Zeeman effect is enhanced for lines in the IR Radiation flux and pulsation amplitudes increase with Radiation flux and pulsation amplitudes increase with
increasing wavelength for cooler stars.increasing wavelength for cooler stars. IR lines can probe different parts of the atmosphere.IR lines can probe different parts of the atmosphere.
2λ
Benefits from the IRBenefits from the IR
Sun continuum contrast between photosphere and Sun continuum contrast between photosphere and TTspot spot == 4250 K:4250 K: ≈ 20% @ 0.6 20% @ 0.6 µµmm ≈ 70% @ 2.2 70% @ 2.2 µµmm
Resolving the telluric absorption lines (intrinsically Resolving the telluric absorption lines (intrinsically narrow narrow ~5 km s~5 km s−1−1) ) Pontoppidan & van Dishoeck, 2004, astroph Pontoppidan & van Dishoeck, 2004, astroph 04056290405629
Zeeman sensitivity: the Fe I line at 1.56 Zeeman sensitivity: the Fe I line at 1.56 µµm m splits by splits by twice the FWHM in 1.5 kG fields (slowly rotating twice the FWHM in 1.5 kG fields (slowly rotating stars): 2-3 times more sensitive than optical lines stars): 2-3 times more sensitive than optical lines (Giampapa PASP 109)(Giampapa PASP 109)