in the Sun and Solar Twins

CNO abundances
in the Sun and
Solar Twins
Jorge Meléndez
Departamento de Astronomia, IAG,
Universidade de São Paulo
Sunset in Paracas, Peru
(c) www.flickr.com/photos/rodrigocampos/
Why are C, N, O (and Ne) important?
After H (X) and He (Y),
they are the most
abundant elements, so
they have a crucial
impact on the mass
fraction of metals Z
(elements heavier than H, He)
X + Y + Z = 1.
H
Asplund et al. 2009
He
C
O
Ne
Mg
N
Al
Na
F
B
Be
Li
Si
Fe
The metallicity Z is important for the morphology
of evolutionary tracks and isochrones
VandenBerg et al. 2007
VandenBerg et al. 2007
Solar models vs. helioseismology
O,
C,
N (dex) + meteoritic
8.86, 7.92, 8.52
8.69, 7.83, 8.43
8.69, 7.83, 8.43 + photospheric
8.66, 7.78, 8.39
E = log(NE/NH) + 12
GS98: Grevesse & Sauval 1998
AGS05 : Asplund et al. 2005
AGSS09 : Asplund et al. 2009
Serenelli et al. 2009
Solar Oxygen Abundance
What is going on with the solar O abundance?
Anders & Grevesse 1989
8.93±0.04
8.76±0.07
Caffau et al.
2008
8.66±0.05
Asplund et al. 2004
8.69±0.05
Asplund et al. 2009
What about carbon ?
Solar carbon abundance
Anders & Grevesse 1989
Caffau et al. 2010
Grevesse & Sauval 1998
Asplund et al. 2009
Asplund et al. 2005
Year
What about nitrogen ?
Solar nitrogen abundance
Anders & Grevesse 1989
Grevesse & Sauval 1998
Caffau et al. 2009
Asplund et al. 2009
Asplund et al. 2005
Year
Why are the Asplund, Grevesse & Sauval
(2005) solar C, N, O abundances very low ?
1) Improvements in the measurements on the solar spectra (blends
with other species).
Forbidden [OI]
line at 6300 A
A(O)=8.69±0.05
3D
Allende Prieto, Lambert,
Asplund (2001)
Why are the Asplund et al. (2005)
solar C, N, O abundances very low ?
2) Improvements in the atomic data (transition probabilities)
3) Improvements in the model atmospheres (3D hydro)
BLEND with NiI (-0.13 dex)‫‏‬
TRANSITION PROBABILITIES
FOR THE [OI] 6300 A line :
Old log gf = -9.78
New log gf = -9.72
Difference in abundance: -0.06 dex
3D-1D: -0.04
After blends + new gf-value + 3D : A(O) = 8,69 dex
Prieto,
Lambert & Asplund
2001,
ApJ, 556,dex
L63
ButAllende
ignoring
3D+blend+better
data,
A(O)=8,92
-
Asplund et al. 2004, A&A, 417, 751
Why Asplund et al. (2005) C, N, O are low?
4) Departures from local thermodynamic equilibrium accounted for (mostly).
Permitted lines: 777 nm OI triplet
A(O)= 8.88
[LTE]
A(O)=8.66, 8.72
[NLTE] SH=0, 1
8.88 [LTE]
8.66 [NLTE]
Center / limb variation of OI
NLTE corrections
~ -0.2 dex
Allende Prieto,
Asplund & Fabiani
Bendicho (2004)‫‏‬
8.72 [NLTE]
NLTE effects on OI 777nm already suggested by Altrock (1968)‫‏‬
Revision of Asplund et al. (2005): new solar CNO
with improved 3D models (Asplund et al. 2009)
The temperature gradient of the Asplund et al. (2005) 3D solar model
atmosphere seem to be too step when compared to observations of
the center-to-limb variation (Ayres et al. 2006; Koesterke et al. 2008).
Disk center
The new 3D model
by Asplund et al.
(2009) has much
improved radiative
transfer and updated
opacities. The new
model is in excellent
agreement with the
center-to-limb
variation observed
in the Sun.
Limb
Asplund et al. (2009)
Latest set of C, N, O abundances from
Asplund, Grevesse, Sauval & Scott (2009)
C = 8.43
N = 7.83
O = 8.69
Excellent agreement between atomic and molecular lines
What about other 3D models ?
Excellent agreement between Stagger
(Asplund et al.) and CO5BOLD (Caffau
et al.) codes
Caffau et al. 2008-10
Asplund et al. 2009
Independent analyses by the Caffau et al. group
(Caffau, Ludwig, Steffen, Freytag et al.)
using 3D CO5BOLD models
Caffau et al.
Asplund
(2008, 2009, 2010)
et al. (2009)
Carbon
8.50+/-0.1
8.43+/-0.05
Nitrogen
7.86+/-0.12
7.83+/-0.05
Oxygen
8.76+/-0.07
8.69+/-0.05
Element
Good agreement on N, but not so good for O and C
Caffau et al. (2009) nitrogen abundance
Used equivalent widths from the literature (Grevesse et al.) + CO5BOLD
3D model + NLTE
Only atomic lines
were analyzed by
Caffau et al.
(Asplund et al.
analyzed atomic and
molecular lines)
Caffau et
al. (2009)
Asplund
et al. (2009)
7.86+/-0.12 7.83+/-0.05
Agreement!
Caffau et al. (2010) carbon abundance
Used their own measurements of equivalent widths + CO5BOLD 3D
model + NLTE
Only atomic lines
were analyzed by
Caffau et al.
(Asplund et al.
used atomic and
molecular lines)
Caffau et
al. (2010)
et al. (2009)
8.5+/-0.1
8.43+/-0.05
Asplund
disagreement!
Main reason for discrepancy is
probably the different set of
equivalent width measurements
used by both groups.
Caffau et al. (2008) oxygen abundance
Used their own measurements of equivalent widths + CO5BOLD 3D
model + NLTE
Only atomic lines
were analyzed by
Caffau et al.
(Asplund et al.
used atomic and
molecular lines)
“Caffau‫‏‬et‫‏‬al.‫‏‬like”
Caffau et
al. (2008)
Asplund et
al. (2009)
8.76+/-0.07
8.69+/-0.05
H.-G. Ludwig, 2012
Main reason for discrepancy is the different set of
equivalent width measurements used by both groups.
disagreement!
Good agreement for N, but who is more likely to
be right (if any) regarding C and O ?
Caffau et al.
Asplund
(2008, 2009, 2010)
et al. (2009)
8.5+/-0.1
8.43+/-0.05
Nitrogen
7.86+/-0.12
7.83+/-0.05
Oxygen
8.76+/-0.07
8.69+/-0.05
Element
Carbon
We urgently need a new independent study
of the photospheric CNO solar abundances
An independent study of C, N, O in the Sun
(Meléndez, in preparation, 2012?)
- Selection‫‏‬of‫‏‬only‫“‏‬best”‫‏‬lines‫(‏‬not‫‏‬always‫‏‬possible)
- Detailed evaluation of blends (mainly CN)
- Careful measurements
- Most recent atomic data
- Using only telluric-corrected solar spectra (red, IR)
- New optical-near IR flux atlas by Wallace et al. 2011
- Complemented in the IR by disk center atlas by
Wallace et al. (1993)
An independent study of C, N, O in the Sun (Meléndez, in prep., 2012?)
Good knowledge of molecular line formation is
needed to take into account blends.
CN is ubiquitous in the solar spectrum
Relative flux
1.00
0.95
0.90
0.85
5000
5500
6000
6500
Wavelength (A)
Meléndez, in preparation
CN is ubiquitous in the solar spectrum
(Meléndez, in prep., 2012?)
Relative flux
1.00
0.95
0.90
0.85
7000
7500
8000
8500
Relative flux
1.00
0.95
0.90
0.85
9000
9500
CN line list from Meléndez & Barbuy (1999)
10000
10050
Wavelength (A)
11000
11050
12000
CN blends for O I triplet
CN blends
must be taken
into account,
otherwise the
equivalent
widths may be
overestimated
or
underestimated
CN CN
(Meléndez, in preparation)
CN
Other blend
CN
CN
CN
Comparison of equivalent widths for O I triplet
Line (A) Asplund Asplund et al. Caffau Caffau
E.W. (A) A(O)
E.W.(A) A(O)
Melendez
E.W.
Melendez
A(O)
7771
71.2
8.68 ?
81.4
8.75
74.3 ± 2.6
8.742
7774
61.8
8.69 ?
68.6
8.74
63.9 ± 0.5
8.743
7776
48.8
8.70 ?
54.2
8.76
50.4 ± 0.5
8.741
average
8.69 dex ?
8.75 dex
8.74 dex
(Meléndez, in preparation)
Asplund et al. E.W. may be
underestimated by 3,5%
Caffau et al. equivalent
widths may be
overestimated by 8,2%
Caution: final result depends on adopted NLTE corrections
(uncertain at least ~ 0,03 dex)
What about the forbidden [OI] lines ?
6300 A line: badly blended with Ni I.
Uncertain correction.
6363 A line: blended with CN.
Very preliminary result, A(O) ~ 8.7
5577 A line: blended with C2.
Very preliminary result, A(O) ~ 8.7
5577 A [OI] line !
Blend by C2 easily constrained by
red side of the feature. O and C
abundances determined at the
same time !
Melendez & Asplund (2008). To be revised‫‏‬
VERY PRELIMINARY
RECOMMENDED OXYGEN
ABUNDANCE (molecular OH lines will
be included later)
Oxygen triplet at 777nm : 8,74 dex
Forbidden [OI] lines 6363, 5577 A : 8,7 dex
Suggested solar O abundance :
Meléndez (in prep.) : 8,72 dex
Caffau et al. 2008: 8,76 dex
Asplund et al. 2009 : 8,69 dex
What about carbon ?

Also, we must be careful about blends with CN lines
 Example : C I lines at 7111,4 and 7113,2 A
CN
CN
CN
CN
CN
CN
CN
CI
CI
CN CN
CN
VERY PRELIMINARY
RECOMMENDED CARBON
ABUNDANCE
(based on permitted lines and
one [C I] line. Molecular lines to be
included later)
Suggested solar C abundance :
Meléndez (in prep.) : 8,40 dex
Caffau et al. 2008: 8,50 dex
Asplund et al. 2009 : 8,43 dex
VERY PRELIMINARY
RECOMMENDED NITROGEN
ABUNDANCE
(based on permitted lines.
Molecular lines to be included later)
Suggested solar N abundance :
Meléndez (in prep.) : 7,82 dex
Caffau et al. 2008: 7,86 dex
Asplund et al. 2009 : 7,83 dex
Summary on C, N, O solar abundances
Caffau et
Element
al. 2008-10
Carbon
Nitrogen
Oxygen
8.50+/0.10
7.86+/0.12
8.76+/0.07
Asplund
et al.
(2009)
8.43+/0.05
7.83+/0.05
8.69+/0.05
Meléndez
(2012 ?)
GS98
8,40
8,52
7,82
7,92
8,72
8,83
Based‫‏‬on‫‏‬the‫‏‬current‫‏‬data‫‏‬it‫‏‬seems‫‏‬unlikely‫‏‬to‫‏‬return‫‏‬to‫‏‬the‫“‏‬high”‫‏‬
Grevesse & Sauval (1998) C, N, O abundances
• Is it correct to assume the solar
abundance pattern for other stars?
• Solar twins can tell us how typical
is the Sun
Sunset in Paracas, Peru
(c) www.flickr.com/photos/rodrigocampos/
Magellan ultra high
Observations of the solar twin 18 Sco
precision study of
solar twins
Magellan 6.5m Clay Telescope
& Mike spectrometer
- R = 65,000
- S/N = 450 per pixel
- coverage 340 – 1000 nm
- Solar spectrum: Vesta
- 3 nights of observations
-
BLUE frame
-
Meléndez et al. 2009
RED frame
32
Example of
Magellan
spectra
(total spectral
coverage
3400 A -1um)
Small part
(597-603nm)
of solar twin &
Sun’s‫‏‬spectra
-
Meléndez et al. 2009
33
Δ‫‏‬abundance:
Sun - <twins>
vs. atomic
number Z
Sun typical :
Δ=0
Sun weird :
Δ ≠‫‏‬0
Our solar
system is not
host by a
typical ‘Sun’
Melendez et al. 2009
34
Sun’s‫‏‬
anomalies
are strongly
correlated to
condensation
temperature
(Tcond) of the
elements!
Correlation is highly
significant
probability ~10-9 to
happen by chance
It’s most likely to win
the lottery
~ 0.08 dex ~ 20%
Condensation temperature
Melendez et al. 2009
35
Condensation in the solar nebula
Mercury
Condensation
Venus
36
The late accreted gas in the convection
zone was deficient in refractories
The late-accreted
gas‫‏‬in‫‏‬the‫‏‬Sun’s‫‏‬
convection zone
was depleted in
refractories which
were used to form
dust, planetesimals
& terrestrial planets
Iron gradient in the inner solar system
37
Either
1) the Sun is
normal in the
volatile C, N, O
AND depleted in
the refractory
elements (e.g.
Fe, Al, Ni)
or
2) the Sun is
normal in the
refractories but
enhanced in the
volatiles (CNO)
~ 0.08 dex ~ 20%
Condensation temperature
Option (1) is most likely correct
Melendez et al. 2009
Results on solar anomalies confirmed
by others.
Our Sun is indeed
chemically
peculiar, perhaps
due to the
formation of
terrestrial planets
The Sun may be
more metal-rich in
its interior!
Meléndez et al. 2012
39
What about the effect of giant planet formation?
16 Cyg pair of solar analogs
16 Cyg A : no planets
16 Cyg B : giant planet
40
16 Cyg B (planet-host) is 0,04 dex more metalpoor in all elements (photospheric abundances)!
Was the missing material used
to form the giant planet around
the solar analog 16 Cyg B ?
Is 16 Cyg B more metal-rich in
its interior ?
41
Conclusions
Solar C, N, O abundances seem intermediate between the
values of Asplund et al (2009) and Caffau et al. (2008,
2009, 2010), although somewhat closer to Asplund et al.
Sun may be more metal-rich in its interior, with refractory
elements about 0,08 dex more abundant than in its
photosphere (terrestrial planet effect)
Sun may be more metal-rich in its interior for ALL
ELEMENTS by another 0,04 dex (giant planet effect)
In summary, Sun may be richer in its interior by 0,12 dex for
refractory elements and 0,04 dex for volatile CNO elements.
It‫‏‬is‫‏‬urgent‫‏‬to‫‏‬estimate‫‏‬the‫‏‬Sun’s‫‏‬abundances‫‏‬in‫‏‬its‫‏‬interior.
42