CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Carbon-Enhanced Metal-Poor stars
Fingerprints of binary evolution and AGB nucleosynthesis
Carlo Abate
in collaboration with
R. Stancliffe
M. Hampel
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
Z. Liu
E. Matrozis
N. Langer
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Very metal-poor stars
H a lo
Bulge
Sun
Disk
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Very metal-poor stars
H a lo
Halo stars:
• Old (& 10 billion years)
• [Fe/H] < −2 (very metal-poor)
Bulge
Sun
Disk
• CEMP (5 − 25%):
→ [C/Fe] > 1
CEMP-s → [Ba/Fe] > 1
[Ba/Eu] > 0
CEMP-r/s → [Eu/Fe] > 1
• Mostly binaries
[X/Y] = log(NX /NY )∗ − log(NX /NY )
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Binary evolution
Long time ago...
MS
MS
1
2
AGB
MS
1
2
CEMP star
white dwarf
MS
1
2
Today.
Asymptotic Giant Branch (AGB) → last nuclear-burning phase of stars with M < 8 M
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
CEMP intersection
metal-poor
stellar population
mixing
CEMP
binary evolution
AGB nucleosynthesis
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
AGB nucleosynthesis: s-process
( s(sizes
i z e s not
n o to
t tscale)
o s c a le )
H
PMZmX
0.75 .
Neutron sources:
13
C(α, n) 16 O
22
Ne(α, n) 25 Mg
0
C-O core
He-shell
envelope
envelope
intershell region
H-shell
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
⇓
Nn ≈ 106 − 1010 cm−3
s-process nucleosynthesis
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
obs-mod
[El/Fe]
Fit to observed abundances: CEMP-s star
HD196944
4
3.5
3
2.5
2
1.5
1
0.5
0
-0.5
-1
1
0.5
0
-0.5
-1
-1.5
-3
(M1 , M2 , MPMZ ) = (1.4, 0.81, 10 ) M⊙
Pb
CO
Sr
Mg
Na
Zr
Y
La
Ba Ce
Er
Sm
Dy
Nd
Eu
[Fe/H] = -2.36
0
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
atomic number
Abate+2015a,b
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
[Ba/Fe] > 1, [Ba/Eu] > 0
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Fit to observed abundances: CEMP-r/s star
CS22948-027
4
-3
M1=1.5, M2=0.61, MPMZ=1x10 , Pi=6.7x10
3.5
3
3
[El/Fe]
2.5
Ba
2
1.5
Na
1
Ce
Nd
Eu
Dy
SrY
Pb
C+N
Pr
Mg
0.5
0
obs-mod
-0.5
-1
1
0.5
0
-0.5
-1
-1.5
Pobs= 427 d,
0
[Fe/H] = -2.41
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85
atomic number
Abate+2015a,b
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
[Ba/Fe] > 1, [Ba/Eu] > 0, [Eu/Fe] > 1
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Best-fit residuals: CEMP-s stars
2
(a)
1.5
residual
1
0.5
0
-0.5
-1
-1.5
C O Mg
Sr Zr
Ba Ce
Eu
Pb
C+N
-2
0
10
20
30
40
50
60
70
80
90
Abate+2015b
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Best-fit residuals: CEMP-r/s stars
2
(b)
1.5
residual
1
0.5
0
-0.5
-1
-1.5
C O Mg
Sr Zr
Ba Ce
Eu
Pb
C+N
-2
0
10
20
30
40
50
60
70
80
90
Abate+2015b
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Independent r− and s−enrichments
3
A
2
s−rich
r/s−rich
100
B
[Eu/Fe]CEMP > [Eu/Fe]C−nor
[Ba/Fe]
C
10-1
1
D
0
0
]=
1 Ba/Eu
[
2
1
10-2
r−rich
[C/Fe] ≤1.0
[C/Fe] >1.0
0
Abate+2016
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
[Ba/Fe] =0.8 ×[Eu/Fe]−0.4
[Ba/Fe] =0.7 ×[Eu/Fe] +1.1
1
[Eu/Fe]
2
3
10-3
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Independent r− and s−enrichments
3
A
2
s−rich
r/s−rich
100
B
[Eu/Fe]CEMP > [Eu/Fe]C−nor
[Ba/Fe]
C
10-1
Dearth of observed stars
1
D
0
0
]=
1 Ba/Eu
[
2
1
10-2
r−rich
[C/Fe] ≤1.0
[C/Fe] >1.0
0
Abate+2016
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
[Ba/Fe] =0.8 ×[Eu/Fe]−0.4
[Ba/Fe] =0.7 ×[Eu/Fe] +1.1
1
[Eu/Fe]
2
3
10-3
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Independent r− and s−enrichments
3
A
2
s−rich
r/s−rich
100
B
[Eu/Fe]CEMP > [Eu/Fe]C−nor
[Ba/Fe]
C
10-1
Dearth of observed stars
1
0
1
10-2
r−rich
0
]=
1 Ba/Eu
[
2
Different Ba-Eu relation
D
[C/Fe] ≤1.0
[C/Fe] >1.0
0
Abate+2016
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
[Ba/Fe] =0.8 ×[Eu/Fe]−0.4
[Ba/Fe] =0.7 ×[Eu/Fe] +1.1
1
[Eu/Fe]
2
3
10-3
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Independent r− and s−enrichments
3
A
2
s−rich
r/s−rich
100
B
[Eu/Fe]CEMP > [Eu/Fe]C−nor
[Ba/Fe]
C
10-1
Dearth of observed stars
1
D
0
1 Ba/E
[
2
[C/Fe] ≤1.0
[C/Fe] >1.0
1
10-2
r−rich
0
u]=
0
Abate+2016
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
[Ba/Fe] =0.8 ×[Eu/Fe]−0.4
[Ba/Fe] =0.7 ×[Eu/Fe] +1.1
1
[Eu/Fe]
2
Different Ba-Eu relation
3
CEMP−r/s
CEMP−s
obs: 26–51%
mod: 22%
10-3
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Independent r− and s−enrichments
3
A
2
s−rich
r/s−rich
100
B
[Eu/Fe]CEMP > [Eu/Fe]C−nor
[Ba/Fe]
C
10-1
Dearth of observed stars
1
D
0
1 Ba/E
[
2
[C/Fe] ≤1.0
[C/Fe] >1.0
1
10-2
r−rich
0
u]=
0
Abate+2016
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
[Ba/Fe] =0.8 ×[Eu/Fe]−0.4
[Ba/Fe] =0.7 ×[Eu/Fe] +1.1
1
[Eu/Fe]
2
Different Ba-Eu relation
3
10
-3
CEMP−r/s
CEMP−s
obs: 26–51%
mod: 22%
CEMP−r/s,[Ba/Fe]>2
CEMP−r/s
73%
4%
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
i-process in AGB stars?
• i–process ⇒ Nn ≈ 1012 − 1015 cm−3
( s(sizes
i z e s not
n oto
t tscale)
o s c a le )
(Cowan+Rose 1977)
0.
H-rich envelope
• proton-ingestion episodes
⇒ 1 H penetrate in He-flash regions
• hydrodynamical symulations find
“something”
(Campbell+2008, Stancliffe+2011, Herwig+2014)
• promising: 1-zone model → intershell
composition + Nn . 1015 cm−3
envelope
He-shell
flash
(Hampel+2016)
intershell
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
H-shell
burning
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Call them CEMP-i stars!
1.0
Residual, RZ
0.5
0.0
0.5
1.0
1.5
individual stars
average i process
average Abate et al. (2015)
30
Sr
50
Ba
Eu
Atomic number
70
80
Hampel+2016, in press (arXiv:1608.08634)
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
Carlo Abate
15–16/11/2016
CEMP stars
AGB nucleosynthesis
Results
AGB i–process
Summary
Carbon-Enhanced Metal-Poor stars
Nuclear Astrophysics in Germany
v ol u ti o
n a ry e
i
b
+
B
AG
nuclear reactions
ti on s
si m u l a
h yd ro
ob s e
rva t
i on s
rs
a
t
- s or y
P
t
M
C E b or a
la
n
Take-home message
Carlo Abate
15–16/11/2016