Abundance patterns of r-process enhanced metal-poor starsSatoshi Honda1, Wako Aoki2, Norbert Christlieb3, Timothy C. Beers4, Michael W.Hannawald2 Toshitaka Kajino2, Hiroyasu Ando2, Paul S. Barklem31 Gunma Astronomical Observatory, 2 National Astronomical Observatory of Japan, 4 Michigan State University, 3 Uppsala Astronomical Observatory

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Nucleosynthesis HHeLiBig Bang Nucleosynthesis

-elements(Mg,Ca,Si)iron-peakStellar nucleosynthesiselementsType II SNeironType Ia SNe

The elements heaver than ironNeutron captures-processBa, Pb, etc.AGB starsr-processEu, Au, Th, etc.still unknown!Burbidge, Burbidge, Fowler, Hoyle 1957

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Type II SNeneutrino windcf. Woosley et al. 1994prompt explosioncf. Sumiyoshi et al. 2001Neutron star mergerscf. Rosswog et al. 2001Collapsars cf. Pruet et al. 2004NSM Freiburghaus et al. 1999SNe Wanajo et al. 2003Collapsar Fujimoto et al. 2006The possible site for the r-process

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Observations of r-process enhanced starsBehavior of Eu abundance as a function of [Fe/H]Large dispersion in [Fe/H] < -2.5 Almost no data in [Fe/H]

Models of galactic chemical evolutionIshimaru et al. 2004[Fe/H]- is important !Argast et al. 200410-30MCescutti et al. 2006Tsujimoto et al. 1999NSMSNeDonder & Vanbeveren 2003Mathews et al. 1992Argast et al. 2004850Msolar

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Observations of r-process enhanced starsBehavior of Eu abundance as a function of [Fe/H]Large dispersion in [Fe/H] < -2.5 Almost no data in [Fe/H]+1 r-I +1>[Eu/Fe]>+0.3Beers & Christlieb 2005

Honda et al. 2004Subaru/HDSFrancois et al. 2007VLT/UVESBarklem et al. 2005Type IIType I

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Detailed analysis of r-II starsUniversal pattern56

Multiple r-process sitesSome 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. 2000Honda et al. 2007CS22892-052CS22892-052HD122563HD88609

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

Subaru/HDS observationsS05B-152) HE2224+0143 HE0432-0923 CS22183-031B (mag) 14.4 15.9 14.2Teff (K)5198 5131 5270[Fe/H] -2.58 -3.19 -2.93[Eu/Fe] +1.05 +1.24 +1.16

Obs. date2005.10.21-23R50,00035505250S/N1001504000Christlieb et al. 2004, Barklem et al. 2005Honda et al. 2004These targets were obtained from HERES.

The spectra of r-II starsHE0432-0923CS22183-031HE2224+0143solarWavelengthFeEuFeFeS/N 100S/N 150S/N 150

Behavior of Eu abundance as a function of metallicityr-II stars exists only in the region of -3.2

abundance patternsThese objects are in agreement with the solar -process pattern.No weak r-process.SrBaEuThLaIr

Abundance patterns of r-II starsCS22892-052, CS31082-001, CS29497-004,CS22183-031, HE2224+0143, HE0432-0923averageEu

The region of Th II 4019 lineHE2224+0143Th IICS22183-031HE0432-0923The spectra of HE0432-0923 may contain the sky-background.CHIt was not completely remove.

Thorium is detected in two objectsThIIThIINdIINdII12CH12CHFeIFeI13CH13CHHE2224+0143CS22183-031Uranium is undetectable.

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

Summary and future workWe 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 -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 UPb abundances.More telescope time in dark night.The number of samples is increased.SEGUE, LAMOST, etc.

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