Abundance patterns of r-process
enhanced metal-poor stars
Satoshi Honda1, Wako Aoki2, Norbert Christlieb3,
Timothy C. Beers4, Michael W.Hannawald2
Toshitaka Kajino2, Hiroyasu Ando2, Paul S. Barklem3
Gunma Astronomical Observatory,
National Astronomical Observatory of Japan,
4 Michigan State University,
3 Uppsala Astronomical Observatory
1
2
Nucleosynthesis
Burbidge, Burbidge, Fowler, Hoyle 1957



H、He、（Li）
 Big Bang Nucleosynthesis
α-elements(Mg,Ca,Si…)、iron-peak
 Stellar nucleosynthesis
 αelements→Type II SNe
 iron→Type Ia SNe
The elements heaver than iron
 Neutron capture

s-process（Ba, Pb, etc.）


AGB stars
r-process（Eu, Au, Th, etc.）

still unknown!
The possible site for the r-process

Type II SNe

neutrino wind


prompt explosion


cf. Sumiyoshi et al. 2001
Neutron star mergers


cf. Woosley et al. 1994
cf. Rosswog et al. 2001
Collapsars

cf. Pruet et al. 2004
NSM Freiburghaus et al. 1999
SNe Wanajo et al. 2003
Collapsar Fujimoto et al. 2006
Observations of r-process enhanced stars

Behavior of Eu abundance
as a function of [Fe/H]


Large dispersion in
[Fe/H] < -2.5
Almost no data in [Fe/H]<-3
Type II SNe
Type I SNe
Honda et al. 2004
Subaru/HDS
Barklem et al. 2005
Francois et al. 2007
VLT/UVES
Models of galactic chemical evolution
10-30M
Mathews et al. 1992
Tsujimoto et al. 1999
Cescutti et al. 2006
Donder & Vanbeveren 2003
Argast et al. 2004
NSM
SNe
8～50Msolar
[Fe/H]＜-３ is important !
Argast et al. 2004
Ishimaru et al. 2004
Observations of r-process enhanced stars

Behavior of Eu abundance
as a function of [Fe/H]



Large dispersion in
[Fe/H] < -2.5
Almost no data in [Fe/H]<-3
r-II star


[Ba/Eu] < 0
r-II ： [Eu/Fe]>+1
r-I ： +1>[Eu/Fe]>+0.3

Beers & Christlieb 2005
Barklem et al. 2005
Type II
Type I
Honda et al. 2004
Subaru/HDS
Francois et al. 2007
VLT/UVES
Detailed analysis of r-II stars

Universal pattern


CS22892-052
56<Z<72
decayed
Th, (and U) line was
detected.

age determination
HE1593-0901
CS31082-001
Sneden et al. 2003
CS29497-004
Frebel et al. 2007
Hill et al. 2002
Christlieb et al. 2004
Multiple r-process sites
CS22892-052

Sneden et al. 2000
CS22892-052

HD122563
HD88609
Honda et al. 2007
Some metal-poor stars
show a significantly
different abundance
pattern from that of
the solar system rprocess abundance
pattern.
This results support
the existence of two
process (main and
weak r-process).
r-II stars discovered by HERES
Hamburg/ESO R-process Enhanced Star survey
←s-process rich stars are also included.
follow-up observations are
required.
Barklem et al. 2005
Subaru/HDS observations
（S05B-152)
HE2224+0143
B (mag)
14.4
Teff (K)
5198
[Fe/H]
-2.58
[Eu/Fe]
+1.05
HE0432-0923
15.9
5131
-3.19
+1.24
These targets were obtained from HERES.
Christlieb et al. 2004, Barklem et al. 2005




Obs. date 2005.10.21-23
R～50,000
3550～5250Å
S/N 100～150＠4000Å
CS22183-031
14.2
5270
-2.93
+1.16
Honda et al. 2004
The spectra of r-II stars
S/N 100
HE0432-0923
S/N 150
CS22183-031
S/N 150
Fe
Eu
Fe
HE2224+0143
Fe
solar
4128
4130
4132
Wavelength（Å）
4134
Behavior of Eu abundance as a function of
metallicity
2
[Eu/Fe]
r-II
1
r-I
0
-1
-4
-3
-2
-1
0
[Fe/H]
r-II stars exists only in the region of
-3.2<[Fe/H]<-2.6.
abundance patterns
1
Sr
HE2224+0143
HE0432-0923
CS22183-031
Ba
log ε
0
Th
Ir
-1
La
-2
40
50
Eu
60
70
Atomic number
80
90
These objects are in agreement with the solar ｒ-process pattern.
No weak r-process.
Abundance patterns of r-II stars
log ε
1
average
0
-1
-2
Eu
40
50
60
70
Atomic number
80
90
CS22892-052, CS31082-001, CS29497-004,
CS22183-031, HE2224+0143, HE0432-0923
The region of Th II 4019 line
1.2
HE0432-0923
1.1
CS22183-031
1
HE2224+0143
0.9
Th II
0.8
4019
CH
4020
The spectra of HE0432-0923 may contain the sky-background.
It was not completely remove.
Thorium is detected in two objects
HE2224+0143
1.02
13CH
FeI
1
CS22183-031
12CH
FeI
1
0.95
NdII
0.96
0.85
4019
4020
12CH
NdII
0.98
ThII
0.9
13CH
ThII
0.94
4019
4020
1
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
3859
0
3859
3859.5
3860
3860.5
Uranium is undetectable.
3859.5
3860
3860.5
Th/Eu as a function of [Fe/H]
HE0432-0923
logε(Th/Eu)
CS30306-132
CS31082-001
0
initial Th/Eu
Sneden et al. 2003
-0.5
HE1523-0901
CS22892-052
-1
-3
-2.5
-2
[Fe/H]

The ratio of Th/Eu show scatter.

The width of the scatter is not so large.
Summary and future work

We confirmed that those objects are r-II stars.


These objects are in agreement with the solar ｒ
-process pattern.




No weak r-process.
The ratio of Th/Eu shows scatter.
Remove the sky-background in the spectra of
HE0432-0923 completely.
Determine the upper limit of U、Pb abundances.


r-II stars exist only in the region of
-2.4 < [Fe/H] < -3.2.
More telescope time in dark night.
The number of samples is increased.

SEGUE, LAMOST, etc.