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Caffau, E.; Bonifacio, P.; Spite, M.; Spite, F.; Monaco, L.; Sbordone, L.; François, P.; Gallagher, A. J.; Plez, B.; Zaggia, S.; Ludwig, H.‐G.; Cayrel, Roger; Koch, Andreas; Steffen, M.; Salvadori, Stefania; Klessen, Ralf S.; Glover, Simon C. O.; Christlieb, N.

doi:10.1051/0004-6361/201629776

Cited by 32 publications

(38 citation statements)

References 42 publications

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“…There are three CEMP-no binary stars on the main sequence (or close to the turn-off), G77−61 with T eff = 4000 K, SDSS J0140+2344 with T eff = 5703 and log g = 4.7, and SDSS J0929+0238 with T eff = 5894 K and log g = 4.5. Another possibility is that SDSS J0929+0238 is a sub-giant branch star with log g = 3.7, but it is argued by Caffau et al (2016) that the main-sequence solution is more likely (unfortunately the Gaia DR2 parallax for this star is uncertain). One of the CEMP-no binary stars, HE 0219−1739, is at the tip of the giant branch.…”

Section: Hertzsprung-russell Diagrammentioning

confidence: 99%

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Binarity among CEMP-no stars: an indication of multiple formation pathways?

Arentsen

Starkenburg

Shetrone

et al. 2019

A&A

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Carbon-enhanced metal-poor (CEMP) stars comprise a large percentage of stars at the lowest metallicities. The stars in the CEMP-no subcategory do not show any s-process enhancement and therefore cannot easily be explained by transfer of carbon and s-process elements from a binary AGB companion. We have performed radial velocity monitoring of a sample of 22 CEMP-no stars to further study the role binarity plays in this type of CEMP star. We find four new binary CEMP-no stars based on their radial velocity variations, thereby significantly enlarging the population of known binaries to a total of eleven. One of the new binary systems is HE 0107−5240, one of the most iron-poor stars known, supporting the binary transfer model for the origin of the abundance pattern of this star. In our sample we find a difference in binary fraction depending on the absolute carbon abundance, with a binary fraction of 47 +15 −14 % for stars with higher absolute carbon abundance and 18 +14 −9 % for stars with lower absolute carbon abundance. This potentially implies a relation between a high carbon abundance and the binarity of a metal-poor star. Although binarity does not equate to mass transfer, there is a possibility that a CEMP-no star in a binary system has been polluted and care has to be taken in the interpretation of their abundance patterns. We furthermore demonstrate the potential of Gaia to discover additional binary candidates.

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Section: Hertzsprung-russell Diagrammentioning

confidence: 99%

“…The ranges on the x-and y-axes have been truncated for clarity, however at least the two largest peaks of the distribution are always shown. SDSS J0929+0238(Caffau et al 2016) and SDSS J1341+4741(Bandyopadhyay et al 2018), we have a sample of eleven CEMP-no binary stars.…”

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confidence: 99%

Binarity among CEMP-no stars: an indication of multiple formation pathways?

Arentsen

Starkenburg

Shetrone

et al. 2019

A&A

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“…The number of extremely and ultra metal-poor stars (with [Fe/H] < −3.0 and [Fe/H] < −4.0, respectively; Beers & Christlieb 2005) analysed in depth has grown a lot in the last decades thanks to laborious efforts to find and characterise them. There are now ∼10 stars known with intrinsic iron-abundances below [Fe/H] = −4.5 (Christlieb, Wisotzki & Graßhoff 2002;Frebel et al 2005;Norris et al 2007;Caffau et al 2013a;Hansen et al 2014;Keller et al 2014;Allende Prieto et al 2015;Bonifacio et al 2015;Allende Prieto et al 2015;Caffau et al 2016) 1 . Some of the most iron-poor stars display abundance patterns that could bear the imprint of the explosion physics of first supernovae.…”

Section: Introductionmentioning

confidence: 99%

The Pristine survey – I. Mining the Galaxy for the most metal-poor stars

Starkenburg

Martín

Youakim

et al. 2017

Monthly Notices of the Royal Astronomical Society

213

219

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We present the Pristine survey, a new narrow-band photometric survey focused on the metallicity-sensitive Ca H & K lines and conducted in the northern hemisphere with the wide-field imager MegaCam on the Canada-France-Hawaii Telescope (CFHT). This paper reviews our overall survey strategy and discusses the data processing and metallicity calibration. Additionally we review the application of these data to the main aims of the survey, which are to gather a large sample of the most metal-poor stars in the Galaxy, to further characterise the faintest Milky Way satellites, and to map the (metal-poor) substructure in the Galactic halo. The current Pristine footprint comprises over 1,000 deg 2 in the Galactic halo ranging from b ∼ 30 • to ∼ 78 • and covers many known stellar substructures. We demonstrate that, for SDSS stellar objects, we can calibrate the photometry at the 0.02-magnitude level. The comparison with existing spectroscopic metallicities from SDSS/SEGUE and LAMOST shows that, when combined with SDSS broad-band g and i photometry, we can use the CaHK photometry to infer photometric metallicities with an accuracy of ∼0.2 dex from [Fe/H] = −0.5 down to the extremely metal-poor regime ([Fe/H] < −3.0). After the removal of various contaminants, we can efficiently select metal-poor stars and build a very complete sample with high purity. The success rate of uncovering [Fe/H] SEGUE < −3.0 stars among [Fe/H] Pristine < −3.0 selected stars is 24% and 85% of the remaining candidates are still very metal poor ([Fe/H]< −2.0). We further demonstrate that Pristine is well suited to identify the very rare and pristine Galactic stars with [Fe/H] < −4.0, which can teach us valuable lessons about the early Universe. . The observations at the Canada-France-Hawaii Telescope were performed with care and respect from the summit of Maunakea which is a significant cultural and historic site.†

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“…The SDSS-based metallicities found by the method of Ludwig et al (2008) are essentially confirmed by the analysis at higher resolution. This method has been very successful and has led to a series of papers that have Article number, page 2 of 14 already been published (Caffau et al 2011a(Caffau et al ,b, 2012(Caffau et al , 2014Bonifacio et al 2015;Caffau et al 2016;Bonifacio et al 2018). The most metal-poor stars are formed out of gas that has been very likely enriched by the ejecta of a single or a few supernovae.…”

Section: Introductionmentioning

confidence: 99%

Chemical analysis of very metal-poor turn-off stars from SDSS-DR12

François

Caffau

Wanajo

et al. 2018

A&A

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Context. The most metal-poor stars are the relics of the early chemical evolution of the Galaxy.Their chemical composition is an important tool to constrain the nucleosynthesis in the first generation of stars. The aim is to observe a sample of extremely metal-poor star (EMP stars) candidates selected from the Sloan Digital Sky Survey Data Release 12 (SDSS DR12) and determine their chemical composition. ⋆ Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme ID 099.D-0576(A). Article number, page 1 of 14 P. François et al.: EMP starsAims. We obtain medium resolution spectra of a sample of six stars using the X-Shooter spectrograph at the Very Large Telescope (VLT) and we used ATLAS models to compute the abundances.Methods. Five stars of the sample have a metallicity [Fe/H] between -2.5 dex and -3.2 dex. We confirm the recent discovery of SDSS J002314.00+030758.0. As a star with an extremely low [Fe/H] ratio. Assuming the α-enhancement [Ca/Fe] = +0.4 dex, we obtain [Fe/H] = -6.1 dex.Results. We could also determine its magnesium abundance and found that this star exhibits a very high ratio [Mg/Fe] ≥ +3.60 dex assuming [Fe/H] = -6.13 dex. We determined the carbon abundance and found A(C) = 6.4 dex. From this carbon abundance, this stars belongs to the lower band of the A(C) -[Fe/H] diagram.

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TOPoS

Cited by 32 publications

References 42 publications

Binarity among CEMP-no stars: an indication of multiple formation pathways?

Binarity among CEMP-no stars: an indication of multiple formation pathways?

The Pristine survey – I. Mining the Galaxy for the most metal-poor stars

Chemical analysis of very metal-poor turn-off stars from SDSS-DR12

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