The Hobby‐Eberly Telescope Chemical Abundances of Stars in the Halo (CASH) Project. I. The Lithium‐,<i>s</i>‐, and<i>r</i>‐enhanced Metal‐poor Giant HKII 17435−00532

Roederer, Ian U.; Frebel, Anna; Shetrone, Matthew; Prieto, C. Allende; Rhee, Jaehyon; Gallino, R.; Bisterzo, S.; Sneden, Christopher; Cowan, J. J.

doi:10.1086/587794

Cited by 53 publications

(65 citation statements)

References 158 publications

(200 reference statements)

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“…For a given metallicity, a spread in the three s-process peaks is observed in stars of spectral type MS, S, C(N) and Ba stars of the Galactic disk (see Abia et al 2001Abia et al , 2002Gallino et al 2005). At low metallicities, highresolution spectroscopic measurements of CEMP-s stars showed an even larger spread (Aoki et al, 2006a;Ivans et al, 2005;Roederer et al, 2008a;Thompson et al, 2008). The observed spread can be interpreted by assuming different s-process efficiencies of these stars, corresponding to a change in the amount of 13 C in the pocket.…”

Section: Theoretical Agb Resultsmentioning

confidence: 98%

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Thesprocess: Nuclear physics, stellar models, and observations

et al. 2011

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Nucleosynthesis in the s process takes place in the He burning layers of low mass AGB stars and during the He and C burning phases of massive stars. The s process contributes about half of the element abundances between Cu and Bi in solar system material. Depending on stellar mass and metallicity the resulting s-abundance patterns exhibit characteristic features, which provide comprehensive information for our understanding of the stellar life cycle and for the chemical evolution of galaxies. The rapidly growing body of detailed abundance observations, in particular for AGB and post-AGB stars, for objects in binary systems, and for the very faint metal-poor population represents exciting challenges and constraints for stellar model calculations. Based on updated and improved nuclear physics data for the s-process reaction network, current models are aiming at ab initio solution for the stellar physics related to convection and mixing processes. Progress in the intimately related areas of observations, nuclear and atomic physics, and stellar modeling is reviewed and the corresponding interplay is illustrated by the general abundance patterns of the elements beyond iron and by the effect of sensitive branching points along the sprocess path. The strong variations of the s-process efficiency with metallicity bear also interesting consequences for Galactic chemical evolution.

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Section: Theoretical Agb Resultsmentioning

confidence: 98%

“…Follow-up high-resolution spectroscopy has been made by the ESO Large Programme First Stars with VLT/UVES (e.g. Sivarani et al, 2006), the Chemical Abundances of Stars in the Halo (CASH) Project (Roederer et al, 2008a), and others (e.g. Aoki et al, 2007).…”

Section: Binary Systems Affected By Mass Transfermentioning

confidence: 99%

Thesprocess: Nuclear physics, stellar models, and observations

et al. 2011

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“…We adopted the line list of Roederer et al (2008Roederer et al ( , 2010, and complemented it with data from the VALD database (Piskunov et al 1995;Ryabchikova et al 1997;Kupka et al 1999Kupka et al , 2000Ryabchikova et al 2015). The line wavelengths and oscillator strengths are given in Table 5 , 6, 7, 8, 9, 10, and 11 .…”

Section: Line List and Solar Abundancesmentioning

confidence: 99%

What is the Milky Way outer halo made of?

Battaglia

North

Jablonka

et al. 2017

A&A

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In a framework where galaxies form hierarchically, extended stellar haloes are predicted to be an ubiquitous feature around Milky Way-like galaxies and to consist mainly of the shredded stellar component of smaller galactic systems. The type of accreted stellar systems are expected to vary according to the specific accretion and merging history of a given galaxy, and so is the fraction of stars formed in-situ versus accreted. Analysis of the chemical properties of Milky Way halo stars out to large Galactocentric radii can provide important insights into the properties of the environment in which the stars that contributed to the build-up of different regions of the Milky Way stellar halo formed. In this work we focus on the outer regions of the Milky Way stellar halo, by determining chemical abundances of halo stars with large present-day Galactocentric distances, >15 kpc. The data-set we acquired consists of high resolution HET/HRS, Magellan/MIKE and VLT/UVES spectra for 28 red giant branch stars covering a wide metallicity range, This appears to suggest a larger contribution in the outer halo of stars formed in an environment with high initial star formation rate and already polluted by asymptotic giant branch stars with respect to inner halo samples.

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“…I already mentioned HE 1424-0241 and its extraordinarily low Si abundance. Perhaps related to this is SDSS J234723.64+010833.4 (Lai et al 2009) (Roederer et al 2008), shows an extraordinarily high lithium abundance (A(Li) = 2.1) and is enhanced in neutron capture elements. It certainly came as a surprise to me to learn that the subgiant BD+44…”

Section: High Resolution Surveysmentioning

confidence: 94%

“…The CASH project (Frebel et al 2008a) is under way at the Hoberly-Eberly telescope and has so far published the first paper of the series (Roederer et al 2008), but see also Roederer et al (2009) in this volume. It is expected to produce highly interesting results in the next few years.…”

Section: High Resolution Surveysmentioning

confidence: 99%

The first galactic stars and chemical enrichment in the halo

Bonifacio

2009

Proc. IAU

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Abstract. The cosmic microwave background and the cosmic expansion can be interpreted as evidence that the Universe underwent an extremely hot and dense phase about 14 Gyr ago. The nucleosynthesis computations tell us that the Universe emerged from this state with a very simple chemical composition: H, 2 H, 3 He, 4 He, and traces of 7 Li. All other nuclei where synthesised at later times. Our stellar evolution models tell us that, if a low-mass star with this composition had been created (a "zero-metal" star) at that time, it would still be shining on the Main Sequence today. Over the last 40 years there have been many efforts to detect such primordial stars but none has so-far been found. The lowest metallicity stars known have a metal content, Z, which is of the order of 10 −4 Z . These are also the lowest metallicity objects known in the Universe. This seems to support the theories of star formation which predict that only high mass stars could form with a primordial composition and require a minimum metallicity to allow the formation of low-mass stars. Yet, since absence of evidence is not evidence of absence, we cannot exclude the existence of such low-mass zero-metal stars, at present. If we have not found the first Galactic stars, as a by product of our searches we have found their direct descendants, stars of extremely low metallicity (Z 10 −3 Z ). The chemical composition of such stars contains indirect information on the nature of the stars responsible for the nucleosynthesis of the metals. Such a fossil record allows us a glimpse of the Galaxy at a look-back time equivalent to redshift z = 10, or larger. The last ten years have been full of exciting discoveries in this field, which I will try to review in this contribution.

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The Hobby‐Eberly Telescope Chemical Abundances of Stars in the Halo (CASH) Project. I. The Lithium‐,s‐, andr‐enhanced Metal‐poor Giant HKII 17435−00532

Cited by 53 publications

References 158 publications

Thesprocess: Nuclear physics, stellar models, and observations

Thesprocess: Nuclear physics, stellar models, and observations

What is the Milky Way outer halo made of?

The first galactic stars and chemical enrichment in the halo

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