A Subaru/High Dispersion Spectrograph Study of Lead (Pb) Abundances in Eight<i>s</i>‐Process Element–rich, Metal‐poor Stars

Aoki, Wako; Ryan, Sean G.; Norris, John E.; Beers, Timothy C.; Ando, Hiroyasu; Tsangarides, Stelios

doi:10.1086/343885

Cited by 190 publications

(264 citation statements)

References 37 publications

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“…(27) Solar abundances reference adopted in the original reference source: Anders & Grevesse (1989, An89), Grevesse et al (1996, Gr96), Grevesse & Sauval (1998, Gr98), Grevesse et al (2000, Gr20), Asplund (2005, As05). references: (1) Cohen et al (2004), (2) Cohen et al (2006), (3) Lucatello et al (2003), (4) Aoki et al (2007), (5) Barklem et al (2005), (6) Lucatello (2003), (7) Christlieb et al (2002), (8) Christlieb et al (2004), (9) Jonsell et al (2006), (10) Norris et al (2007), (11) Cohen et al (2008), (12) Goswami et al (2006), (13) Frebel et al (2007), (14) Frebel et al (2005), (15) Aoki et al (2006), (16) Frebel et al (2006), (17) Cohen et al (2003), (18) Johnson & Bolte (2002), (19) Tsangarides (2005), (20) Aoki et al (2002c), (21) Aoki et al (2002d), (22) …”

Section: Open Questionsmentioning

confidence: 99%

A holistic approach to carbon-enhanced metal-poor stars

Masseron

Johnson²,

Plez

et al. 2010

A&A

235

462

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Context. Carbon-enhanced metal-poor (CEMP) stars are known to have properties that reflect the nucleosynthesis of the first lowand intermediate-mass stars, because most have been polluted by a now-extinct AGB star. Aims. By considering abundances in the various CEMP subclasses separately, we try to derive parameters (such as metallicity, mass, temperature, and neutron source) characterising AGB nucleosynthesis from the specific signatures imprinted on the abundances, and separate them from the impact of thermohaline mixing, first dredge-up, and dilution associated with the mass transfer from the companion. Methods. To place CEMP stars in a broader context, we collect abundances for about 180 stars of various metallicities (from solar to [Fe/H] = −4), luminosity classes (dwarfs and giants), and abundance patterns (e.g. C-rich and poor, Ba-rich and poor), from both our own sample and the literature. Results. We first show that there are CEMP stars that share the properties of CEMP-s stars and CEMP-no stars (which we refer to as CEMP-low-s stars). We also show that there is a strong correlation between Ba and C abundances in the s-only CEMP stars. This represents a strong detection of the operation of the 13 C neutron source in low-mass AGB stars. For the CEMP-rs stars (seemingly enriched with elements from both the s-and r-processes), the correlation of the N abundances with abundances of heavy elements from the 2nd and 3rd s-process peaks bears instead the signature of the 22 Ne neutron source. Since CEMP-rs stars also exhibit O and Mg enhancements, we conclude that extremely hot conditions prevailed during the thermal pulses of the contaminating AGB stars. We also note that abundances are not affected by the evolution of the CEMP-rs star itself (especially by the first dredge-up). This implies that mixing must have occurred while the star was on the main sequence, and that a large amount of matter must have been accreted so as to trigger thermohaline mixing. Finally, we argue that most CEMP-no stars (with neutron-capture element abundances comparable to non-CEMP stars) are likely the extremely metal-poor counterparts of CEMP neutron-capture-rich stars. We also show that the C enhancement in CEMP-no stars declines with metallicity at extremely low metallicity ([Fe/H] < −3.2). This trend is not predicted by any of the current AGB models.

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Section: Open Questionsmentioning

confidence: 99%

A holistic approach to carbon-enhanced metal-poor stars

Masseron

Johnson²,

Plez

et al. 2010

A&A

235

462

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“…Lead was detected in SDSS J1349-0229 and SDSS J0912+0216. The line list from Aoki et al (2002) was used in the analysis.…”

Section: Neutron-capture Elementsmentioning

confidence: 99%

Three carbon-enhanced metal-poor dwarf stars from the SDSS

Behara

Bonifacio

Ludwig

et al. 2010

A&A

135

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Context. The origin of carbon-enhanced metal-poor stars enriched with both s and r elements is highly debated. Detailed abundances of these types of stars are crucial to understand the nature of their progenitors. Aims. The aim of this investigation is to study in detail the abundances of SDSS J1349-0229, SDSS J0912+0216 and SDSS J1036+1212, three dwarf CEMP stars, selected from the Sloan Digital Sky Survey. Methods. Using high resolution VLT/UVES spectra (R ∼ 30 000) we determine abundances for Li, C, N, O, Na, Mg, Al, Ca, Sc, Ti, Cr, Mn, Fe, Co, Ni and 21 neutron-capture elements. We made use of CO 5 BOLD 3D hydrodynamical model atmospheres in the analysis of the carbon, nitrogen and oxygen abundances. NLTE corrections for Ci and Oi lines were computed using the Kiel code. Results. We classify SDSS J1349-0229 and SDSS J0912+0216 as CEMP-r+s stars. SDSS J1036+1212 belongs to the class CEMPno/s, with enhanced Ba, but deficient Sr, of which it is the third member discovered to date. Radial-velocity variations have been observed in SDSS J1349-0229, providing evidence that it is a member of a binary system. Conclusions. The chemical composition of the three stars is generally compatible with mass transfer from an AGB companion. However, many details remain difficult to explain. Most notably of those are the abundance of Li at the level of the Spite plateau in SDSS J1036+1212 and the large over-abundance of the pure r-process element Eu in all three stars.

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“…These, along with a handful of other metal-poor stars with moderately enhanced r-process elements (þ0:5 ½r-process/Fe þ1:0, e.g., Westin et al 2000;Johnson & Bolte 2001;Cowan et al 2002), display remarkably similar abundance patterns in the range 56 Z < 76, all apparently in good agreement with the solar-system r-process component. In addition, some of the neutron-capture-enhanced, metal-poor stars exhibit abundance patterns associated with s-process nucleosynthesis (e.g., Norris, Ryan, & Beers 1997;Van Eck et al 2001;Aoki et al 2002;Lucatello et al 2003). These efforts are having a large collective impact on studies on the origin of the neutron-capture elements in the Galaxy (e.g., Ishimaru & Wanajo 1999;Fields, Truran, & Cowan 2002;Qian & Wasserburg 2002), and on the underlying physics and astrophysical sites of the r-and s-processes (e.g., Gallino et al 1998;Wanajo et al 2002Wanajo et al , 2003Schatz et al 2002;Truran et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic Studies of Extremely Metal‐Poor Stars with the Subaru High Dispersion Spectrograph. I. Observational Data

Honda

Aoki

Ando

et al. 2004

ASTROPHYS J SUPPL S

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We have obtained high-resolution (R ' 50; 000 or 90,000), high-quality (S= N k 100) spectra of 22 very metalpoor stars ([Fe/H P À 2:5) with the High Dispersion Spectrograph fabricated for the 8.2 m Subaru Telescope. The spectra cover the wavelength range from 3500 to 5100 8; equivalent widths are measured for isolated lines of numerous elemental species, including the -elements, the iron-peak elements, and the light and heavy neutron-capture elements. Errors in the measurements and comparisons with previous studies are discussed. These data will be used to perform detailed abundance analyses in the following papers of this series. Radial velocities are also reported and are compared with previous studies. At least one moderately r-process-enhanced metal-poor star, HD 186478, exhibits evidence of a small-amplitude radial velocity variation, confirming the binary status noted previously. During the course of this initial program, we have discovered a new moderately r-process-enhanced, very metal-poor star, CS 30306À132 ([Fe/H ¼ À2:4; [Eu/Fe ¼ þ0:85), which is discussed in detail in the companion paper.

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A Subaru/High Dispersion Spectrograph Study of Lead (Pb) Abundances in Eights‐Process Element–rich, Metal‐poor Stars

Cited by 190 publications

References 37 publications

A holistic approach to carbon-enhanced metal-poor stars

A holistic approach to carbon-enhanced metal-poor stars

Three carbon-enhanced metal-poor dwarf stars from the SDSS

Spectroscopic Studies of Extremely Metal‐Poor Stars with the Subaru High Dispersion Spectrograph. I. Observational Data

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