1. Limits on Solar CNO From Helioseismology @Special Session 13 IAU - XXVIII GA Aldo Serenelli Institute of Space Sciences (CSIC-IEEC) Bellaterra, Spain Beijing – 28.08.12SpS 13 - IAUGA

2. Outline Beijing – 28.08.12SpS 13 - IAUGA  High and low solar metallicity: why metals matter  Helioseismic probes of solar structure: impact of metallicity differences – degeneracy with opacity  Deriving abundances from helioseismology  Opacities  Opacity independent probes of solar metallicity

3. Solar Abundances Solar abundances log E X = log (N X /N H )+12 Two paradigmatic sets Differences  New 3-D hydrodynamic models of solar atmosphere  NLTE treatment of some elements  Refined selection of lines (e.g. identification of blends) Reduction of CNO(Ne) ~ 30-40% Beijing – 28.08.12SpS 13 - IAUGA GS98: Grevesse & Sauval (1998) AGSS09: Asplund et al. (2009) GS98 or GN93 representative of high-Z comp. AGSS09 or AGS05 representative of low-Z comp.

4. Metals Matter in Solar Interior Beijing – 28.08.12SpS 13 - IAUGA  Large contribution to rad. opacity k (between 30 to 80%) O most important individual contribution Radiative temperature gradient  temperature stratification in radiative interior  Contribution (minor) to EOS  Changes in nuclear rates, particularly CNO rates

5. Metals & Opacity Effect of individual elements on radiative opacity Heavy (eg. Fe, Si) : solar core  helium Intermediate (Ne, O): radiat. envelope  R CZ Light (C, N): convective envelope Beijing – 28.08.12SpS 13 - IAUGA Helioseismology largely insensitive to C & N

6. Helioseismic Probes Beijing – 28.08.12SpS 13 - IAUGA Acoustic modes --- structural quantities: p, r, G 1, c 2 can be obtained “directly” Modes characterized by ( n,l,m ) Different modes sample the solar interior differently Inner turning-point radius determined by

7. Helioseismic Probes Beijing – 28.08.12SpS 13 - IAUGA Inversions: take two independent variables from the pool (p, r, c 2, G 1 ) e.g. c 2, r or c 2, G 1 and construct radial profiles

8. Sound and Density Profiles Beijing – 28.08.12SpS 13 - IAUGA Large deviation in sound speed due to mismatch in CE boundary, determined by condition

9. Convective Envelope Boundary Beijing – 28.08.12SpS 13 - IAUGA R CZ =0.713±0.001 R 8 Basu & Antia 2004 (and many before)

10. Surface Helium Abundance Beijing – 28.08.12SpS 13 - IAUGA Partial ionization zones leave imprints on G 1 HeII dip used to determine surface Y (modulo EOS & other contributions e.g. OIII) Y S in the range 0.24-0.25 Adopt Y S =0.2485±0.0034

11. Solar Abundance Problem Beijing – 28.08.12SpS 13 - IAUGA Summarizing results Helioseismology favours higher solar metallicity (GS98-like)

12. Other Helioseismic Probes Beijing – 28.08.12SpS 13 - IAUGA Using combinations of frequencies Roxburgh & Vorontsov 2003 Large separationsSmall separations

13. Other Helioseismic Probes Beijing – 28.08.12SpS 13 - IAUGA Using directly combinations of frequencies Roxburgh & Vorontsov 2003 Basu et al. 2007 Small separations ratios insensitive to surface effects

14. Other Helioseismic Probes Beijing – 28.08.12SpS 13 - IAUGA Deficit due to low helium core abundance in low-Z models (also degenerate with opacities)

15. Abunds from Seismic constraints Beijing – 28.08.12SpS 13 - IAUGA Sensitivity of Y S, R CZ and dc to element abundances R CZ -R CZ (Hel) Y S -Y S (Hel) R/Rsun Change Ne/O ratio, keep Y S & R CZ O= 8.86±0.04 Ne=8.15±0.17 Fe= 7.50±0.05 Using either model as reference Not surprisingly very close to GN93 or GS98 values

16. Abunds from Seismic constraints Beijing – 28.08.12SpS 13 - IAUGA A more integrated approach including neutrino fluxes (pp, pep, 8 B, 7 Be) and a radial profile for the sound speed (not just ) Two treatments of opacity uncertainty (CNO)-(CNO) AGSS09 = 0.18±0.02 dex (NeMg)-(NeMg) AGSS09 = 0.10±0.05 (SiS)-(SiS) AGSS09 = 0.12±0.03 (Fe)-(Fe) AGSS09 = 0.00±0.16 dk/k=0.025 (CNO)-(CNO) AGSS09 = 0.15±0.03 (NeMg)-(NeMg) AGSS09 = 0.17±0.06 (SiS)-(SiS) AGSS09 = 0.05±0.06 (Fe)-(Fe) AGSS09 = -0.02±0.05 k OP -k OPAL Villante et al. in prep. Differences in results highlight necessity for proper opacity uncertainties

17. Solar Abundance Problem Beijing – 28.08.12SpS 13 - IAUGA However... from solar modeling point of view, all previous results are degenerate with stellar opacities Low-Z model + increased k All helioseismic probes discussed before are recovered if opacity is increased Christensen Dalsgaard et al 2009

18. How Much Opacity Needed? Beijing – 28.08.12SpS 13 - IAUGA Dk~20-30% at RCZ Dk~3-5% at the core Christensen Dalsgaard et al. 2009

19. How Much Opacity Available? Beijing – 28.08.12SpS 13 - IAUGA Dk~2-3% at RCZ Dk~1-% at the core OP vs OPALOPAS vs OP (blue) Badnell et al. 2005 Blancard et al. 2012 Large differences for indiv. elements but compensation Dk~2% at RCZ Dk<4% at any radii

20. Opacity Independent Probe Beijing – 28.08.12SpS 13 - IAUGA Partial ionization of metals at R < 0.98R  CV NeIX OVII NVI Difference in G 1 depends on EOS Li et al. 2007

21. Opacity Independent Probe Beijing – 28.08.12SpS 13 - IAUGA Partial ionization of metals at R < 0.98R  CV NeIX OVII NVI Some sensitivity on individual elements, e.g. C & O

22. Solar Neutrinos Beijing – 28.08.12SpS 13 - IAUGA 8 B precisely determined 3% - used as a thermometer Combining expressions for 13 N and 15 O, including experimental sensitivity & neutrino oscillations (Haxton & Serenelli 2008)  SSM only used as a reference point (and exponents)  Exponents ‘robust’ to variations in solar model inputs  Uncertainty dominated by experimental (S 17 & S 1 14 ) contributions “Perfect” CN measurement gives central C+N to about 12% Using Borexino upper limit for F( 13 N+ 15 O): X(C+N) Borexino < 0.0072 X(C+N) GS98 = 0.0048 -- X(C+N) AGSS09 = 0.0039

23. Summary Beijing – 28.08.12SpS 13 - IAUGA Solar models with high-Z (GS98-GN93; CNO but also others) is much more consistent with seismic inferences of solar structure than low-Z models Almost all seismic probes of metallicity are degenerate with radiative opacities Exception is G 1 due to partial ionization of metals – signal small and interpretation depends on EOS Opacity changes needed >> than systematic differences, no actual information on internal uncertainties Inversion of the problem: using seismic probes to extract composition leads to results similar to high-Z compositions. Treatment of opacity uncertainties unclear and crucial Solar neutrinos for core C+N can be competitive in 2-3 years