1. Why We Need SONG Sarbani Basu Yale University

2. Image courtesy J. Christensen-Dalsgaard

3. Observing in Velocity: Lower Noise

4. Observing in Velocity: non-zero l=3 response

5. 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.

7. Surface term in Standard Solar Models

9. Same interior physics could still give rise to different surface terms

10. What happens with deficient physics?

11. Low Frequencies will help in modelling by defining the surface term

12. Surface Term and Echelle Diagrams

13. What we observe

16. What happens if we do not have low-frequency modes

18. Add Lower frequencies

19. What else? Define other diagnostics

21. l=3 modes will allow inversions A Hermitian Eigenvalue problem, therefore use the variational principle:

22. How we invert frequecies

23. The mode-sets

24. The solutions

25. The Averaging Kernels

26. Cross-term kernels

28. Lower Turning Points of modes

29. Add Low-Frequency modes to l=0,1,2 sets

30. The Best Kepler Modeset (so far) Low frequency modes will made a huge difference

31. 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