Are inputs to standard solar models correct?

OR The problem with solar abundances

Sarbani BasuYale Univesity

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

Just how bad is the situation?

Solar properties:

YCZ= 0.2485±0.0034 (Basu & Antia 1995,2004) RCZ=0.713±0.001R0 (Basu & Antia 1997, 2004)

Models from Bahcall, Basu & Serenelli (2005)

GS model: YCZ= 0.243, RCZ=0.715

AGS model: YCZ= 0.230, RCZ=0.729

Models from Bahcall, Basu, Pinsonneault & Serenelli (2005)

BP04+ (Z/X=0.0176): YCZ= 0.238, RCZ=0.726

BP04+21% (Z/X=0.0176, opacity increased by 21% at 2.18x106K) : YCZ= 0.239, RCZ=0.713

BP04+11% (Z/X=0.0176, opacity increased by 11% between 2 and 5 MK) : YCZ= 0.243, RCZ=0.716

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: YCZ= 0.229, RCZ=0.728

AGS, OP : YCZ= 0.230, RCZ=0.729 GS, OPAL : YCZ= 0.243, RCZ=0.715 GS, OP : YCZ= 0.243, RCZ=0.714

Diffusion rates?

From Delahaye & Pinsonneault 2006

Can we get acceptable solar models with the new abundances if all other inputs are changed within their errors?

From Bahcall, Serenelli & Basu 2006

What if one element’s abundance is underestimated?

Candate: NeonWhy? (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)

Closer to the surface: The ionization zones

Lin, Antia, Basu (2007, submitted)

Revisit Neon

Lin, Antia, Basu (2007, submitted)

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:

)(

)(

)(

,d

d

d

4

)()64()(

)(

2,2,

,1,

0,2,

2,1,2,

n

ndr

n

r

r

r

cnlnd

nd

l

llll

lnlnl

R

ln

lll

lnlnll

(Small separations)

(large separations)

(separation ratios)

Small separations

Separation ratios

From Basu et al. (2006)

Models shown earlier

Can we determine Z from helioseismology?GS

AGS

Z= 0.0187 to 0.0239

Error 12% to 19%Chaplin et al. 2007, submitted

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

Z can be determined from the ionization zones too:

r

c

Gm

rrW

d

d)(

22

ZSun=0.017± 0.002

Antia & Basu (2006)

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.