1. Abundance patterns of r-process enhanced metal-poor stars Satoshi Honda 1, Wako Aoki 2, Norbert Christlieb 3, Timothy C. Beers 4, Michael W.Hannawald 2 Toshitaka Kajino 2, Hiroyasu Ando 2, Paul S. Barklem 3 1 Gunma Astronomical Observatory, 2 National Astronomical Observatory of Japan, 4 Michigan State University, 3 Uppsala Astronomical Observatory

2. Nucleosynthesis 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! Burbidge, Burbidge, Fowler, Hoyle 1957

3. Type II SNe neutrino wind cf. Woosley et al. 1994 prompt explosion cf. Sumiyoshi et al. 2001 Neutron star mergers 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 The possible site for the r-process

4. 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 Honda et al. 2004 Subaru/HDS Francois et al. 2007 VLT/UVES Barklem et al. 2005 Type II SNeType I SNe

5. Models of galactic chemical evolution Ishimaru et al. 2004 [Fe/H] ＜ - ３ is important ! Argast et al. 2004 10-30M Cescutti et al. 2006 Tsujimoto et al. 1999 NSM SNe Donder & Vanbeveren 2003 Mathews et al. 1992 Argast et al. 2004 8 ～ 50M solar

6. 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 Honda et al. 2004 Subaru/HDS Francois et al. 2007 VLT/UVES Barklem et al. 2005 Type IIType I

7. Detailed analysis of r-II stars Universal pattern 56<Z<72 Th, (and U) line was detected. age determination Sneden et al. 2003 Hill et al. 2002 Christlieb et al. 2004 CS22892-052 CS31082-001 CS29497-004 Frebel et al. 2007 HE1593-0901 decayed

8. Multiple r-process sites Some metal-poor stars show a significantly different abundance pattern from that of the solar system r- process abundance pattern. This results support the existence of two process (main and weak r-process). Sneden et al. 2000 Honda et al. 2007 CS22892-052 HD122563 HD88609

9. r-II stars discovered by HERES ← s-process rich stars are also included. follow-up observations are required. Barklem et al. 2005 Hamburg/ESO R-process Enhanced Star survey

10. Subaru/HDS observations （ S05B-152) HE2224+0143 HE0432-0923 CS22183-031 B (mag) 14.4 15.9 14.2 Teff (K) 5198 5131 5270 [Fe/H] -2.58 -3.19 -2.93 [Eu/Fe] +1.05 +1.24 +1.16 Obs. date 2005.10.21-23 R ～ 50,000 3550 ～ 5250 Å S/N 100 ～ 150 ＠ 4000 Å Christlieb et al. 2004, Barklem et al. 2005 Honda et al. 2004 These targets were obtained from HERES.

11. The spectra of r-II stars HE0432-0923 CS22183-031 HE2224+0143 solar Wavelength （Å） Fe Eu Fe S/N 100 S/N 150

12. Behavior of Eu abundance as a function of metallicity r-II stars exists only in the region of -3.2<[Fe/H]<-2.6.

13. abundance patterns These objects are in agreement with the solar ｒ -process pattern. No weak r-process. Sr Ba Eu Th La Ir

14. Abundance patterns of r-II stars CS22892-052, CS31082-001, CS29497-004, CS22183-031, HE2224+0143, HE0432-0923 average Eu

15. The region of Th II 4019 line HE2224+0143 Th II CS22183-031 HE0432-0923 The spectra of HE0432-0923 may contain the sky-background. CH It was not completely remove.

16. Thorium is detected in two objects Th II Nd II 12 CH Fe I 13 CH HE2224+0143CS22183-031 Uranium is undetectable.

17. Th/Eu as a function of [Fe/H] The ratio of Th/Eu show scatter. The width of the scatter is not so large. CS22892-052 CS31082-001 CS30306-132 initial Th/Eu Sneden et al. 2003 HE1523-0901 HE0432-0923

18. Summary and future work We confirmed that those objects are r-II stars. r-II stars exist only in the region of -2.4 < [Fe/H] < -3.2. 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. More telescope time in dark night. The number of samples is increased. SEGUE, LAMOST, etc.