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Abundance patterns of r-process enhanced metal-poor stars

Explore nucleosynthesis, stellar evolution, and observational data to uncover the origins of r-process enhanced stars and understand their unique abundance patterns in relation to the solar system. Investigate the presence of main and weak r-process components in metal-poor stars.

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Abundance patterns of r-process enhanced metal-poor stars

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  1. 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 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 The possible site for the r-process SNe Wanajo et al. 2003 Collapsar Fujimoto et al. 2006 NSM Freiburghaus et al. 1999

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

  5. Models of galactic chemical evolution 10-30M Tsujimoto et al. 1999 Mathews et al. 1992 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

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

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

  8. Multiple r-process sites CS22892-052 • 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 CS22892-052 HD122563 HD88609 Honda et al. 2007

  9. 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

  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. date2005.10.21-23 • R～50,000 • 3550～5250Å • S/N100～150＠4000Å These targets were obtained from HERES. Honda et al. 2004 Christlieb et al. 2004, Barklem et al. 2005

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

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

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

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

  16. Thorium is detected in two objects HE2224+0143 CS22183-031 13CH FeI 12CH 13CH 12CH FeI NdII NdII ThII ThII Uranium is undetectable.

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

  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.

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