# Why We Need SONG

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21-Jan-2016

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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 Presentation

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Why We Need SONGSarbani BasuYale University

Image courtesyJ. Christensen-Dalsgaard Observing in Velocity: Lower Noise

Can go to lower frrequencies3Observing in Velocity: non-zero l=3 response

The PESKY SURFACE TERMWe do not know how to model the near surface layers of stars. Problems

convection/turbulenceAtmospheres Low temperature opacitiesTreatment of radiation in optically thin layers..

These problems introduce a frequency dependent offset between observed and modelled frequencies.

Surface term in Standard Solar Models

Model S, BS05_op, gs_eddi

7

Same interior physics could still give rise to different surface terms

What happens with deficient physics?

Low Frequencies will help in modelling by defining the surface termSurface Term and Echelle Diagrams

12What we observe

What we observe

What happens if we do not have low-frequency modes

What happens if we do not have low-frequency modes

Add Lower frequencies

What else? Define other diagnostics

l=3 modes will allow inversions

A Hermitian Eigenvalue problem, therefore use the variational principle:

How we invert frequeciesThe mode-sets

The solutions

The Averaging Kernels

Cross-term kernels

Lower Turning Points of modes

Add Low-Frequency modes to l=0,1,2 setsThe Best Kepler Modeset (so far)

Low frequency modes will made a huge differenceConclusionsLow-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