1. New Trends of Physics 2005, Hokkaido University, March 1
Nucleosynthesis in Extremely Metal-Poor Stars of Low and Intermediate Mass and Identification of Population III Survivors
Takuma Suda1,
Takanori Nishimura1,
Nobuyuki Iwamoto2,
Masayuki Aikawa3,
Masayuki Y. Fujimoto1
and
Icko Iben Jr.4
1 : Hokkaido University
2 : Japan Atomic Energy
Research Institute
3 : Universite Libre de
Buruxelles
4 : University of Illinois

2. Topics Characteristics of Extremely Metal-Poor Stars
AGB Evolution of Extremely Metal-Poor Stars
Nucleosynthesis in Ultra Metal-Poor Stars

3. 1. Characteristics of Extremely Metal-Poor Stars

4. Extremely Metal-Poor (Iron-Poor) Stars
EMP : Extremely Metal-Poor stars
[Fe/H] < -3 : ~100 stars
[Fe/H] < -3.5 : ~10 stars
No stars for - 5 < [Fe/H] < - 4
2 stars below [Fe/H] = - 5
UMP : Ultra Metal-Poor stars

5. Motivations
We aim to …
Get information about the chemical history of the early universe.
Provide the prescription to discuss the effect of internal/external pollution on the surface chemical composition of stars during their long lives.
Identify the first generation stars

6. Characteristics in EMP
Large fraction (25%) of carbon stars (C/O > 1) compared with the Population I & II stars (a few %)
Large scattering in the abundances of s-process elements around [Fe/H] ~ -3 2 2 1
[Ba/Fe]
[C/Fe] -1 -4 -3 -2 -1 -2 -4
-3.5 -3
-2.5 -2
[Fe/H]
[Fe/H]
Aoki et al.(2002)

7. The Explanation for the Origin of UMP
Approach from the origin of elements
Origin of light alpha elements, N, and Na
Origin of s-process elements

8. 2. AGB Evolution of Extremely Metal-Poor Stars

9. AGB Evolution of EMP He C+O H+He He He-Flash Convection
Surface Convection

10. He-Flash Driven Deep Mixing in EMP
He flash driven convection
Bottom of Hydrogen burning shell
Bottom of surface convection
Hydrogen Mixing
(only for [Fe/H] < -2.5) Mr
12C(p,γ)13N(e+ν)13C(α,n)16O
& Neutron Capture Nucleosynthesis
time

11. He-FDDM in EMP (2) Helium shell flash phase 3rd dredge-up He-FDDM
of n-capture
elements
He-FDDM
H-Flash
Convection
Dredge-up
of C, N
H mixing
H mixing
Surface
convection
Mr : mass coordinate
storage of
n-capture
elements
He/H
interface
13C mixing
He-Flash
Convection
With/Without splitting the convection
Time

12. 3. Nucleosynthesis in Ultra Metal-Poor Stars

13. Reaction Network 65 isotopes Z n-capture p-capture α-capture βdecay A
27Si
28Si
29Si
30Si
25Al
26Al
27Al
28Al
29Al
22Mg
23Mg
24Mg
25Mg
26Mg
20Na
21Na
22Na
23Na
18Ne
19Ne
20Ne
21Ne
22Ne
17F
18F
19F Z
14O
15O
16O
17O
18O
12N
13N
14N
15N
65 isotopes
11C
12C
13C
14C
n-capture
p-capture
α-capture
βdecay
Bao et al. (2000) 8B 9B
10B
11B
NACRE
Caughlan & Fowler (1988)
7Be
8Be
9Be
6Li
7Li
Tables of Isotopes
3He
4He
6He A
developed by M. Aikawa and T. Nishimura 1H 2H 3H n

14. Extended Network
926 nuclei and ~1700 reactions (mainly n-capture and beta decay) are computed with the program developed by N. Iwamoto.
Change of composition is determined by giving abundance of 34S and neutron density for each time step.

15. Initial Models of He-Shell Flash
One zone approximation of He-shell flashes
8.5
(Description : Aikawa, Fujimoto, Kato 2001)
Input Parameters
Z=0, Z☉
13C/12C=
τmix= sec
log T
8.15
102
Time (sec)
1016

16. Pb Sr Ba Abundance Distribution normalized by carbon abundance
13C/12C=0.02
dtmix=1011(sec)
13C/12C=0.001
dtmix=1011(sec)
Magic number of neutron
(50,82,126) Pb Sr Ba
[Sr/Ba] < -0.5

17. Conclusions
Final abundances of light elements (Na, Mg, Al) depend on the degree of mixing and these are well reproduced for HE0107, HE1327.
Sr of HE1327 may have another source.
Initial metals effectively absorb neutrons and are converted into Pb.
The determination of Pb abundance is crucial for the identification of Population III survivors.