why we need song
DESCRIPTION
Why We Need SONG. Sarbani Basu Yale University. Image courtesy J. Christensen-Dalsgaard. Observing in Velocity: Lower Noise. Observing in Velocity: non-zero l =3 response. We do not know how to model the near surface layers of stars. Problems convection/turbulence Atmospheres - PowerPoint PPT PresentationTRANSCRIPT
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Why We Need SONG
Sarbani BasuYale University
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Image courtesyJ. Christensen-Dalsgaard
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Observing in Velocity: Lower Noise
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Observing in Velocity: non-zero l=3 response
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THE PESKY SURFACE TERM
We do not know how to model the near surface layers of stars. Problems
(1)convection/turbulence(2)Atmospheres (3)Low temperature opacities(4)Treatment of radiation in optically thin layers(5)…..
These problems introduce a frequency dependent offset between observed and modelled frequencies.
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Surface term in Standard Solar Models
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Same interior physics could still give rise to different surface terms
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What happens with deficient physics?
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Low Frequencies will help in modelling by defining the surface term
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Surface Term and Echelle Diagrams
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What we observe
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What we observe
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What happens if we do not have low-frequency modes
aν
obsν0
⎛
⎝
⎜⎜⎜
⎞
⎠
⎟⎟⎟
b
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What happens if we do not have low-frequency modes
aν
obsν0
⎛
⎝
⎜⎜⎜
⎞
⎠
⎟⎟⎟
b
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Add Lower frequencies
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What else? Define other diagnostics
Separation Ratio: r
02=
ν(0,n+1) −ν(2,n)ν(1,n+1) −ν(1,n)
Separation Ratio: r
13=
ν(1,n+1) −ν(3,n)ν(2,n+1) −ν(2,n)
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2nd differences: δ 2ν =ν(n−1, l) −2ν(n, l) +ν(n+1, l)
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l=3 modes will allow inversions
A Hermitian Eigenvalue problem, therefore use the variational principle:
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How we invert frequecies
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The mode-sets
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The solutions
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The Averaging Kernels
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Cross-term kernels
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Lower Turning Points of modes
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Add Low-Frequency modes to l=0,1,2 sets
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The Best Kepler Modeset (so far)
Low frequency modes will made a huge difference
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Conclusions
• Low-frequency modes will help us to model stars better.
• l=3 modes will help us invert frequency differences between a star and its model to determine how good a model is.
• SONG will be able to provide both low-frequency modes, as well as l=3 modes
ERGO
WE NEED SONG