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Limits on Solar CNOFrom Helioseismology
@Special Session 13IAU - XXVIII GA
Aldo SerenelliInstitute of Space Sciences (CSIC-IEEC)
Bellaterra, Spain
Beijing – 28.08.12 SpS 13 - IAUGA
Outline
Beijing – 28.08.12 SpS 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
Solar Abundances
Solar abundances
log EX= log (NX/NH)+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 – 28.08.12 SpS 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.
Metals Matter in Solar Interior
Beijing – 28.08.12 SpS 13 - IAUGA
Large contribution to rad. opacity (between 30 to 80%)
O most important individual contributionRadiative temperature gradient temperature stratification in radiative interior
Contribution (minor) to EOS
Changes in nuclear rates, particularly CNO rates
Metals & Opacity
Effect of individual elements on radiative opacity
Heavy (eg. Fe, Si) : solar core helium
Intermediate (Ne, O): radiat. envelope RCZ
Light (C, N): convective envelope
Beijing – 28.08.12 SpS 13 - IAUGA
Helioseismology largely insensitive to C & N
Helioseismic Probes
Beijing – 28.08.12 SpS 13 - IAUGA
Acoustic modes --- structural quantities: p, , 1, c2 can beobtained “directly”Modes characterized by (n,l,m) Different modes sample the solar interior differentlyInner turning-point radius determined by
Helioseismic Probes
Beijing – 28.08.12 SpS 13 - IAUGA
Inversions: take two independent variables from the pool (p, , c2, 1) e.g. c2,
or c2,
and construct radial profiles
Sound and Density Profiles
Beijing – 28.08.12 SpS 13 - IAUGA
Large deviation in sound speed due to mismatch in CE boundary, determined by condition
Convective Envelope Boundary
Beijing – 28.08.12 SpS 13 - IAUGA
RCZ=0.713±0.001 R8
Basu & Antia 2004 (and many before)
Surface Helium Abundance
Beijing – 28.08.12 SpS 13 - IAUGA
Partial ionization zonesleave imprints on 1
HeII dip used to determinesurface Y(modulo EOS & othercontributions e.g. OIII)
YS in the range 0.24-0.25
Adopt YS=0.2485±0.0034
Solar Abundance Problem
Beijing – 28.08.12 SpS 13 - IAUGA
Summarizing results
Helioseismology favours higher solar metallicity (GS98-like)
Other Helioseismic Probes
Beijing – 28.08.12 SpS 13 - IAUGA
Using combinations of frequencies
Roxburgh & Vorontsov 2003
Large separations Small separations
Other Helioseismic Probes
Beijing – 28.08.12 SpS 13 - IAUGA
Using directly combinations of frequencies
r
dr
dr
dc
nr
nrR
nn
nn
nn
nn
0
0,0,1
3,11,13
1,11,
2,10,02
)(
)(
Roxburgh & Vorontsov 2003
Basu et al. 2007
Small separations ratiosinsensitive to surfaceeffects
Other Helioseismic Probes
Beijing – 28.08.12 SpS 13 - IAUGA
Deficit due to low helium core abundance in low-Z models(also degenerate with opacities)
Abunds from Seismic constraints
Beijing – 28.08.12 SpS 13 - IAUGA
Sensitivity of YS, RCZ and c to element abundances
RCZ-RCZ(Hel)
YS-Y
S(H
el)
R/Rsun
Change Ne/O ratio, keep YS & RCZ
O= 8.86±0.04Ne=8.15±0.17Fe= 7.50±0.05
Using either model as referenceNot surprisinglyvery close to GN93or GS98 values
Abunds from Seismic constraints
Beijing – 28.08.12 SpS 13 - IAUGA
A more integrated approach including neutrino fluxes (pp, pep,8B, 7Be) and a radial profile for the sound speed (not just <dc>)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
=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
OP-OPAL
Villante et al. in prep.
Differences in results highlight necessity for proper opacity uncertainties
Solar Abundance Problem
Beijing – 28.08.12 SpS 13 - IAUGA
However...
from solar modeling point of view, all previous results are degenerate with stellar opacities
Low-Z model + increased
All helioseismic probes discussed before are recovered if opacity is increased
Christensen Dalsgaard et al 2009
How Much Opacity Needed?
Beijing – 28.08.12 SpS 13 - IAUGA
~20-30% at RCZ~3-5% at the core
Christensen Dalsgaard et al. 2009
How Much Opacity Available?
Beijing – 28.08.12 SpS 13 - IAUGA
~2-3% at RCZ~1-% at the core
OP vs OPAL OPAS vs OP (blue)
Badnell et al. 2005 Blancard et al. 2012
Large differences for indiv. elements but compensation~2% at RCZ<4% at any radii
Opacity Independent Probe
Beijing – 28.08.12 SpS 13 - IAUGA
Partial ionization of metals at R < 0.98R
CV
NeIX
OVII
NVI
Difference in 1 depends on EOS
Li et al. 2007
Opacity Independent Probe
Beijing – 28.08.12 SpS 13 - IAUGA
Partial ionization of metals at R < 0.98R
Some sensitivity on individual elements, e.g. C & O
Solar Neutrinos
Beijing – 28.08.12 SpS 13 - IAUGA
8B precisely determined 3% - used as a thermometerCombining expressions for 13N and 15O, 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 (S17 & S1 14) contributions“Perfect” CN measurement gives central C+N to about 12%
Using Borexino upper limit for (13N+15O): X(C+N)Borexino< 0.0072
X(C+N)GS98= 0.0048 -- X(C+N)AGSS09= 0.0039
Summary
Beijing – 28.08.12 SpS 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 withradiative opacities
Exception is 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 compositionleads to results similar to high-Z compositions. Treatment of opacityuncertainties unclear and crucial
Solar neutrinos for core C+N can be competitive in 2-3 years