1. Are inputs to standard solar models correct? OR The problem with solar abundances Sarbani Basu Yale Univesity

2. Why are we asking this question?  Standard solar models had shown a remarkable agreement with the Sun. BUT  The new, lowered, solar abundances spoil the agreement. Older abundances : Grevesse & Sauval (1998), Z/X=0.0229 New abundances: Asplund et al. (2005), Z/X=0.0165

3. Just how bad is the situation? Solar properties: Y CZ = 0.2485±0.0034 (Basu & Antia 1995,2004) R CZ =0.713±0.001R 0 (Basu & Antia 1997, 2004) Models from Bahcall, Basu & Serenelli (2005) GS model: Y CZ = 0.243, R CZ =0.715 AGS model: Y CZ = 0.230, R CZ =0.729

4. Models from Bahcall, Basu, Pinsonneault & Serenelli (2005) BP04+ (Z/X=0.0176): Y CZ = 0.238, R CZ =0.726 BP04+21% (Z/X=0.0176, opacity increased by 21% at 2.18x10 6 K) : Y CZ = 0.239, R CZ =0.713 BP04+11% (Z/X=0.0176, opacity increased by 11% between 2 and 5 MK) : Y CZ = 0.243, R CZ =0.716

5. Two recalculations of opacities (OP, Badnell et al., 2005; LEDCOP, Neuforge-Verheecke et al. 2001) agree with OPAL to within 3% at the CZ base. Models from Bahcall, Serenelli & Basu (2005) AGS, OPAL: Y CZ = 0.229, R CZ =0.728 AGS, OP : Y CZ = 0.230, R CZ =0.729 GS, OPAL : Y CZ = 0.243, R CZ =0.715 GS, OP : Y CZ = 0.243, R CZ =0.714

6. Diffusion rates?

7. From Delahaye & Pinsonneault 2006

8. Can we get acceptable solar models with the new abundances if all other inputs are changed within their errors? From Bahcall, Serenelli & Basu 2006

9. What if one element’s abundance is underestimated? Candate: Neon Why? (1) Adds to opacity at CZ base temperatures (2) No photospheric lines of Neon. Abundance determined by assuming a Ne/O ratio (solar value 0.15). Models from Bahcall, Basu & Serenelli (2005)

10. Relationship between structure and frequencies: A Hermitian Eigenvalue problem, therefore use the variational principle :

11. Why do Asplund et al. think that their results are reliable? 3D models more realistic than 1D model atmospheres. No free parameters needed to model effects of turbulence on lines (i.e., do not need parameters for micro- and nacro-turbulence). Line bisectors match data. Line profiles from 3D models fit better.

12. Different lines of the same species give less dispersion of abundances when fitted with 3D models. Heavy-element abundance of the Sun now in line with those of other young objects.

13. Closer to the surface: The ionization zones Lin, Antia, Basu (2007, submitted)

14. Revisit Neon Lin, Antia, Basu (2007, submitted)

15. What about the solar core? Cannot invert very well, but can compare combinations of frequencies that are sensitive to the structure of the core? Data used: BiSON low degree frequencies obtained with a 4752-day time series. Frequency combinations: (Small separations) (large separations) (separation ratios)

16. Small separations Separation ratios From Basu et al. (2006) Models shown earlier

17. Can we determine Z from helioseismology? GS AGS Z= 0.0187 to 0.0239 Error 12% to 19% Chaplin et al. 2007, submitted

18. We can get a better estimate of the average mean molecular weight in the core GS AGS  c = 0.7209 to 0.7231 Error 0.5% Average GS = 0.7203 Average AGS= 0.7088 Chaplin et al. 2007, submitted

19. Z can be determined from the ionization zones too: Z Sun =0.017± 0.002 Antia & Basu (2006)

20. Conclusions  It is premature to declare the inputs to solar structure calculations incorrect  A lot more work needs to be done in determining the solar abundances.