Abundances and kinematics of carbon-enhanced metal-poor stars in the Galactic halo

Hansen, C. J.; Hansen, T. T.; Koch, Andreas; Beers, T. C.; Nordström, B.; Placco, Vinicius M.; Andersen, J.

doi:10.1051/0004-6361/201834601

Cited by 53 publications

(64 citation statements)

References 98 publications

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“…10), but SDSS J0222-0313 is clearly too rich in Ba and Sr to be a CEMP-no star. This misclassification, still compatible with the classification by Hansen et al (2019) within the uncertainties, is a clear symptom that this star has an uncommon chemical pattern. The s-process nucleosynthesis in rotating massive stars is able to produce this level of [Sr/Ba] ratio (Frischknecht et al 2016;Limongi & Chieffi 2018), but rotating massive stars eject Sr and Ba only during supernovae explosion.…”

Section: Discussionsupporting

confidence: 70%

“…With all their limitations, classifications of CEMP stars are very useful to place stars with similar chemical properties in the same sub-class; for example, the Spite et al (2013) division in A(C) is very useful for distinguishing CEMP-no from other CEMP stars. With the classification by Hansen et al (2019) A&A 628, A46 2019we can quite confidently separate a CEMP-s from a CEMP-r star. But these classificaitons can also be used to help recognise strange objects, which can be identified by their misfits.…”

Section: Discussionmentioning

confidence: 82%

“…In Fig. 9, we compared the abundances of C, O, Sr, and Ba with respect to Fe derived for SDSS J0222-0313 with stars analysed by Hansen et al (2016aHansen et al ( , 2019, which are mostly CEMP stars. SDSS J0222-0313 is always in the upper part of each panel, but still consistent with the comparison sample stars.…”

Section: Discussionmentioning

confidence: 99%

“…This is a CEMP star, rich in heavy elements that we classify as a CEMP-s star, according to the scheme of Beers & Christlieb (2005). With its high [Sr/Ba] ratio, according to Hansen et al (2019) it should be a CEMP-no star, but taking into account the uncertainties in the Sr and Ba determination, it would fit in their CEMP-s sub-class.…”

Section: A46 Page 1 Of 10mentioning

confidence: 99%

“…More recently, Hansen et al (2019; see their Table 6) suggested a new classification, efficient in discriminate CEMP-s and CEMP-r, based on the [Sr/Ba] ratio. Both Beers & Christlieb (2005) and Hansen et al (2019) introduced the sub-classes to all CEMP stars, without a closer look at the C abundance. Their classifications do not subdivide CEMP stars according to the absolute C abundance, A(C) 2 .…”

Section: Introductionmentioning

confidence: 99%

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The CEMP star SDSS J0222–0313: the first evidence of proton ingestion in very low-metallicity AGB stars?

Caffau

Monaco

Bonifacio

et al. 2019

A&A

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Context. Carbon-enhanced metal-poor (CEMP) stars are common objects in the metal-poor regime. The lower the metallicity we look at, the larger the fraction of CEMP stars with respect to metal-poor stars with no enhancement in carbon. The chemical pattern of CEMP stars is diversified, strongly suggesting a different origin of the C enhancement in the different types of CEMP stars. Aims. We selected a CEMP star, SDSS J0222–0313, with a known high carbon abundance and, from a low-resolution analysis, a strong enhancement in neutron-capture elements of the first peak (Sr and Y) and of the second peak (Ba). The peculiarity of this object is a greater overabundance (with respect to iron) of the first s-process peak than the second s-process peak. Methods. We analysed a high-resolution spectrum obtained with the Mike spectrograph at the Clay Magellan 6.5 m telescope in order to derive the detailed chemical composition of this star. Results. We confirmed the chemical pattern we expected; we derived abundances for a total of 18 elements and significant upper limits. Conclusions. We conclude that this star is a carbon-enhanced metal-poor star enriched in elements produced by s-process (CEMP-s), whose enhancement in heavy elements is due to mass transfer from the more evolved companion in its asymptotic giant branch (AGB) phase. The abundances imply that the evolved companion had a low main sequence mass and it suggests that it experienced a proton ingestion episode at the beginning of its AGB phase.

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Section: Discussionsupporting

confidence: 70%

Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: A46 Page 1 Of 10mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The CEMP star SDSS J0222–0313: the first evidence of proton ingestion in very low-metallicity AGB stars?

Caffau

Monaco

Bonifacio

et al. 2019

A&A

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Heavy elements

Hansen

2022

Exp Astron

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How are the heavy elements formed? This has been a key open question in physics for decades. Recent direct detections of neutron star mergers and observations of evolved stars show signatures of chemical elements in the blue range of their spectra that bear witness of recent nuclear processes that led to heavy element production. The formation of heavy elements typically takes place through neutron-capture reactions creating radioactive isotopes, which following beta-decay turn into the stable isotopes we today can measure indirectly in the surfaces of cool, low-mass stars or meteoritic grains. The conditions (such as the neutron density or entropy) of these n-capture reactions remain to date poorly constrained, and only through a multidisciplinary effort can we, by combining and comparing observations, experiments, and theoretical predictions, improve on one of the top 10 most important open physics questions posed at the turn of the century. This emphasises the need for detailed observations of the near-UV to blue wavelength region. The shortage of spectrographs and hence spectra covering this range with high-resolution and high signal-to-noise has for decades played a limiting factor in our understanding of how heavy elements form in the nuclear reactions as well as how they behave in the stellar surfaces. With CUBES (Cassegrain U-Band Efficient Spectrograph) we can finally improve the observations, by covering the crucial blue range in more remote stars and also achieve a higher signal-to-noise ratio (SNR). This is much needed to detect and accurately deblend the absorption lines and in turn derive more accurate and precise abundances of the heavy elements.

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The CUBES science case

et al. 2022

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We introduce the scientific motivations for the development of the Cassegrain U-Band Efficient Spectrograph (CUBES) that is now in construction for the Very Large Telescope. The assembled cases span a broad range of contemporary topics across Solar System, Galactic and extragalactic astronomy, where observations are limited by the performance of current ground-based spectrographs shortwards of 400 nm. A brief background to each case is presented and specific technical requirements on the instrument design that flow-down from each case are identified. These were used as inputs to the CUBES design, that will provide a factor of ten gain in efficiency for astronomical spectroscopy over 300-405 nm, at resolving powers of $$R~\sim$$ R ∼ 24,000 and $$\sim$$ ∼ 7,000. We include performance estimates that demonstrate the ability of CUBES to observe sources that are up to three magnitudes fainter than currently possible at ground-ultraviolet wavelengths, and we place its predicted performance in the context of existing facillities.

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Abundances and kinematics of carbon-enhanced metal-poor stars in the Galactic halo

Cited by 53 publications

References 98 publications

The CEMP star SDSS J0222–0313: the first evidence of proton ingestion in very low-metallicity AGB stars?

The CEMP star SDSS J0222–0313: the first evidence of proton ingestion in very low-metallicity AGB stars?

Heavy elements

The CUBES science case

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