Missing s-Process and
light r-residuals
Roberto Gallino
Work in progress (since 25 years)
in collaboration with
Sara Bisterzo, Cesar Domingo Pardo, Michael Heil,
Franz Kaeppeler, Oscar Straniero
VISTARS,3rd Winter Workshop on Nuclear Astrophysics RUSSBACH,
SPRING? Feb 5-10, 2007
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The classical analysis of the s-process is commonly used
to predict the s-percentage isotope contributions to the
solar system, and by default of their r-process residuals
(calculated as r = 1 - s).
Three s-process components were anticipated by the
classical analysis: the weak, the main, and the strong scomponent
This first-order prediction still remains valid for close-by
nuclides. However the main s-component is far from
being a unique process!
Comparison of AGB stellar model calculations at various
metallicities with spectroscopic observations of different
stellar populations clearly demonstrates the vaste
multiplicity of s-process components.
Major evidence is provided by low-metallicity C-rich and
s-process rich stars (the Lead stars).
Termination of the s-process
208Pb
and 209Bi
are at the
termination point
of the
s-fluence
(Ratzel et al. PRC
70 065803 2004)
With a primary-like 13C-pocket, lead becomes the major
s-process product at low metallicity
S-process in AGB stars
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AGB stars and the two sources of neutrons
The choice of 13C-pocket guided by observations
Lead stars at low metallicities
Primary light elements
Lead stars with s and r-process enhancements
The Sr, Y, Zr, PUZZLE
Na at low metallicity and choice of the initial mass
C-rich and no s-process rich AGB stars
The r-process as the mirror image of the r-process
(Tout est simple rien n’est simple; Simpe’)
Reproduction of the Solar MainComponent
(Gallino et al. 1998; Arlandini et al.1999)
13C-pocket
choice:
• artificially introduced
• ad hoc modulated
• constant Pulse by Pulse
AND METALLICITY
[Fe/H] = -0.3
CASE ST
Metallicity
dependence of
the s-process
distribution, seen
through the
abundance of the
three s-peaks
Busso, Gallino, Wasserburg, ARAA 1999
The Sr, Y and
Zr puzzle: how
many n-capture
components?
[Sr/Fe], [Y/Fe] and
[Zr/Fe] vs [Fe/H]
Travaglio et al.,
ApJ 601, 864 (2004).
GCE - GALACTIC
CHEMICAL EVOLUTION
OF THE S PROCESS
96Ru
98Ru
99Ru
100Ru
101Ru
102Ru
103Ru
104Ru
5.52
1.88
12.7
12.6
17.0
31.6
39.3d
18.7
97Tc
98Tc
99Tc
100Tc
2.6My
4.2My
213ky
15s
92Mo
94Mo
95Mo
96Mo
97Mo
98Mo
99Mo
100 Mo
14.8
9.25
15.9
16.7
9.55
24.1
66h
9.63
93Nb
94Nb
95Nb
96Nb
100
20ky
35d
23h
90Zr
91Zr
92Zr
93Zr
94Zr
95Zr
96Zr
97Zr
51.5
11.2
17.2
1.5My
17.4
64d
2.80
17h
89 Y
90 Y
91 Y
92 Y
100
64h
59d
3.5h
84 Sr
86 Sr
87 Sr
88 Sr
89 Sr
90 Sr
91 Sr
0.56
9.86
7.00
82.6
51d
29y
9.5h
85Rb
86Rb
87Rb
88Rb
72.2
19d
27.8
18m
85Krm
82 Kr
83 Kr
84 Kr
4.5h
86 Kr
87 Kr
11.6
11.5
57.0
85Krg
17.3
76m
11y
[Ba/Fe], [Eu/Fe] and [Ba/Eu] vs [Fe/H]
Travaglio et al.,
ApJ 521, 691 1999
TP-AGB Stars
Example: 5 Msun Z = 0.02
THE ROLE OF NEW CROSS SECTIONS
|Arl99
KR 80| 0.117
KR 82| 0.371
KR 86| 0.270
RB 87| 0.354
SR 86| 0.470
SR 87| 0.503
SR 88| 0.922
Y 89| 0.920
ZR 90| 0.722
ZR 94| 1.082
ZR 96| 0.550
MO96| 1.061
|bao00 |bao07 |
| 0.117| 0.109|
| 0.353| 0.299|
| 0.199| 0.182|
| 0.211| 0.266|
| 0.555| 0.596|
| 0.555| 0.586|
| 0.859| 1.023|
| 0.928| 0.987|
| 0.702| 0.726|
| 1.073| 1.112|
| 0.633| 0.704|
| 0.996| 1.034|
| Arl99
RU100| 0.953
PD104| 1.057
CD110| 0.970
SN116| 0.944
TE122| 0.879
TE123| 0.895
TE124| 0.908
XE128| 0.817
XE130| 0.829
|bao00 | bao07 |
| 0.969| 1.002|
| 1.094| 1.126|
| 0.993 | 1.065|
| 0.953 | 0.853|
| 0.857| 0.891|
| 0.880| 0.912|
| 0.899| 0.921|
| 1.125| 1.029|
| 1.066| 1.099|
(CONTINUES)
|Arl99
BA134| 0.982
BA136| 1.002
BA137| 0.655
BA138| 0.857
CE140| 0.832
ND142| 0.924
SM148| 0.966
SM150| 1.000
GD152| 0.883
GD154| 0.953
DY160| 0.874
ER164| 0.827
YB170| 1.011
|bao00 |bao07 |
| 1.161 | 1.055 |
| 1.067 | 1.055 |
| 0.650 | 0.621 |
| 0.911 | 0.890 |
| 0.920 | 0.892 |
| 0.989 | 0.967 |
| 0.920 | 1.011 |
| 1.000 | 1.000 |
| 0.853 | 0.738 |
| 0.922 | 0.910 |
| 0.929 | 0.892 |
| 0.765 | 0.742 |
| 0.907 | 0.884 |
|Arl99
LU176| 1.250
HF176| 0.965
TA180| 0.488
W 180| 0.046
RE187| 0.002
OS186| 0.972
OS187| 0.815
PT192 | 0.981
HG198| 1.024
PB204| 0.943
PB206| 0.578
PB207| 0.637
PB208| 0.345
BI209| 0.049
|bao00 |ba007 |
| 1.231| 0.912|
| 1.007 | 1.122|
| 0.762 | 0.750|
| 0.055| 0.056|
| 0.086| 0.086|
| 1.208| 1.045|
| 0.495| 0.512|
| 0.718| 0.793|
| 1.092| 1.085|
| 0.973| 0.917|
| 0.607| 0.659|
| 0.633| 0.575|
| 0.428| 0.413|
| 0.060| 0.055|
STRONG COMPONENT AND NEW FRANEC MODELS
Using the neutron capture network and the FRANEC
MODELS available in 1999, for Pb208 the strong component
gives 60% of solar abundance, while the
main component provided 34%.
Similarly to what we did in Arlandini1999, we can simulate
the strong component as the average of 1.5 and 3 Msun AGB
models and ST case, but for [Fe/H]=-1.3 (Z1m3).
Pb206
Pb207
Pb208
Bi209
Arl99 GCE99
6369 6%
10850 18%
55673 60%
16830 14%
Z1M3
7%
12%
60%
18%
• Now to the major point. It concerns the updated AGB
FRANEC models at low metallicity with respect to the ones
used by Travaglio1999.
• In 1999, we had FRANEC models for M=1.5 Msun and
Zsolar only, while for M = 3 Msun we had two FRANEC
models for Zsolar and Z=1/3 Zsolar (i.e. [Fe/H]=-0.5). For
M=1.5Msun and metallicities lower than solar, we used the
same Zsolar stellar structure (in particular the He shell mass
zoning, and the development of the various thermal
convective pulses). For M=3Msun we used the Zsolar stellar
structure in the range Zsolar to 1/2 Zsolar, while for lower
metallicities we used the M3 1/3Zsolar stellar structure.
• Today, FRANEC codes for M=1.5 and 3Msun and
metallicity of Z=Zsolar, 1/3Zsolar and 1/6Zsolar are
available.
• What is important in order to deduce the sprocess composition
• in the He shell after each thermal pulse (TP)
is:
• (i) the choice of the C13-pocket strength,
• (ii) the temperature trend in the TP
• (iii) the mass involved by each TP and the
overlap factor between adjacent TPs.
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Z = Zsolar
TP Mshell r
5
1.75 0.58
10 1.45 0.50
15 1.25 0.45
20 1.07 0.43
25 0.87 0.42
30 0.82 0.42
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Z=1/3 Zsolar
TP Mshell r
5
1.44
0.55
10 1.26 0.42
15 1.10 0.36
20 0.96 0.34
25 0.85 0.34
30 0.80 0.34
Z=1/6Zsolar
M=3Msun NEW
TP
5
10
15
20
25
30
r
Mshell
2.15 0.49
2.05 0.34
1.95 0.26
1.70 0.25
1.65 0.24
1.50 0.23
• Apart from some differences in the overlapping factors, and
in the number of TPs, which have their own impact in the syields, the most important parameter is the mass of the
convective He shell, Mshell, which corresponds very
closely to the He shell mass.
• For M=1.5Msun, passing from the Zsolar case we only had
in 1999 to the NEW Z=1/6Zsolar, the Mshell values
increase by about a factor 1.15. For M=3Msun, passing
from the Z=1/3Zsolar model (the lower we had in 1999) to
the NEW model at Z=1/6Zsolar typically the Mshell value
doubles!
• Now, comparing here below the production factors obtained
at [Fe/H]=-1.3 (AVER of M=1.5 and M=3 Msun) using the
old AGB models, and the old neutron capture network, with
the AGB model used today, and the same will3 network,
we obtain the following results:
• STRONG+MAIN COMPONENT RESULTS:
• Adding this contribution to the one of the updated
main component we obtain:
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| GCE Tr1999
pb206 | 63.9
pb207 | 82.2
pb208 | 94.8
bi209 | 19.0
| newGCE|
| 64.3 |
| 71.9 |
| 75.6 |
| 15.7 |
THE END OF THE DAY