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View article: Chemical abundances of 20 barium stars from the OHP spectra
Chemical abundances of 20 barium stars from the OHP spectra Open
Based on the high resolution and high signal-to-noise spectra, we derived the chemical abundances of 20 elements for 20 barium (Ba-) stars. For the first time, the detailed abundances of four sample stars, namely HD 92482, HD 150430, HD 15…
View article: Chemical abundances of 20 barium stars from the OHP spectra
Chemical abundances of 20 barium stars from the OHP spectra Open
Based on the high resolution and high signal-to-noise spectra, we derived the chemical abundances of 20 elements for 20 barium (Ba-) stars. For the first time, the detailed abundances of four sample stars, namely HD 92482, HD 150430, HD 15…
View article: Detailed analysis of a sample of field metal-poor N-rich dwarfs
Detailed analysis of a sample of field metal-poor N-rich dwarfs Open
Aims. The aim of this work is to compare the detailed chemical composition of the field N-rich dwarf stars to the second-generation stars of globular clusters (GCs) in order to investigate the hypothesis that they originated in GCs. Method…
View article: Be, V, and Cu in the halo star CS 31082-001 from near-UV spectroscopy
Be, V, and Cu in the halo star CS 31082-001 from near-UV spectroscopy Open
The ‘First Stars’ programme revealed the metal-poor halo star CS 31082-001 to be r-process and actinide rich, including the first measurement of a uranium abundance for an old star. To better characterize and understand such rare objects, …
View article: Detailed investigation of two high‐speed evolved Galactic stars
Detailed investigation of two high‐speed evolved Galactic stars Open
The study of metal poor stars provides clarification and knowledge about the primordial Universe. Specially, halo stars provide explanations of the nature of the first generations of stars and the nucleosynthesis in the metal‐poor regime. …
View article: TOPoS
TOPoS Open
Context. The goal of the Turn-Off Primordial Stars survey (TOPoS) project is to find and analyse turn-off (TO) stars of extremely low metallicity. To select the targets for spectroscopic follow-up at high spectral resolution, we relied on …
View article: The <i>Gaia</i> RVS benchmark stars
The <i>Gaia</i> RVS benchmark stars Open
Context. The Radial Velocity Spectrometer (RVS) on board the Gaia satellite is not provided with a wavelength calibration lamp. It uses its observations of stars with known radial velocity to derive the dispersion relation. To derive an ac…
View article: High-speed stars: Galactic hitchhikers
High-speed stars: Galactic hitchhikers Open
Context. The search for stars born in the very early stages of the Milky Way star formation history is of paramount importance in the study of the early Universe since their chemistry carries irreplaceable information on the conditions in …
View article: Reviving old controversies: is the early Galaxy flat or round?
Reviving old controversies: is the early Galaxy flat or round? Open
We analysed a set of very metal-poor stars, for which accurate chemical abundances have been obtained as part of the ESO Large Program “First stars” in the light of the Gaia DR2 data. The kinematics and orbital properties of the stars in t…
View article: Reviving old controversies: is the early Galaxy flat or round? Investigations into the early phases of the Milky Way formation through stellar kinematics and chemical abundances
Reviving old controversies: is the early Galaxy flat or round? Investigations into the early phases of the Milky Way formation through stellar kinematics and chemical abundances Open
We analyse a set of very metal-poor stars for which accurate chemical abundances have been obtained as part of the ESO Large Program "First stars" in the light of the Gaia DR2 data. The kinematics and orbital properties of the stars in the…
View article: 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? Open
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 c…
View article: Be and O in the ultra metal-poor dwarf 2MASS J18082002-5104378: the Be–O correlation
Be and O in the ultra metal-poor dwarf 2MASS J18082002-5104378: the Be–O correlation Open
Context. Measurable amounts of Be could have been synthesised primordially if the Universe were non-homogeneous or in the presence of late decaying relic particles. Aims. We investigate the Be abundance in the extremely metal-poor star 2MA…
View article: TOPoS V: Abundance ratios in a sample of very metal-poor turn-off stars
TOPoS V: Abundance ratios in a sample of very metal-poor turn-off stars Open
Extremely metal-poor stars are keys to understand the early evolution of our Galaxy. The ESO large programme TOPoS has been tailored to analyse a new set of metal-poor turn-off stars, whereas most of the previously known extremely metal-po…
View article: TOPoS
TOPoS Open
Context. Extremely metal-poor stars are keys to understand the early evolution of our Galaxy. The ESO large programme TOPoS has been tailored to analyse a new set of metal-poor turn-off stars, whereas most of the previously known extremely…
View article: A CEMP-no star in the ultra-faint dwarf galaxy Pisces II
A CEMP-no star in the ultra-faint dwarf galaxy Pisces II Open
Aims. A probable carbon enhanced metal-poor (CEMP) star, Pisces II 10694, was discovered recently in the ultra-faint (UFD) galaxy Pisces II . This galaxy is supposed to be very old, suspected to include dark matter, and likely formed the b…
View article: Gaia confirms that SDSS J102915+172927 is a dwarf star
Gaia confirms that SDSS J102915+172927 is a dwarf star Open
The Gaia Data Release 2 provides a parallax of 0.734+/-0.073 mas for SDSS J102915+172927, currently the most metal-poor known object. This parallax implies that it is dwarf star, ruling out the scenario that it is a subgiant. The subgiant …
View article: Abundance patterns of the light neutron-capture elements in very and extremely metal-poor stars
Abundance patterns of the light neutron-capture elements in very and extremely metal-poor stars Open
Aims. The abundance patterns of the neutron-capture elements in metal-poor stars provide a unique record of the nucleosynthesis products of the earlier massive primitive objects. Methods. We measured new abundances of so-called light neutr…
View article: Chemical analysis of very metal-poor turn-off stars from SDSS-DR12
Chemical analysis of very metal-poor turn-off stars from SDSS-DR12 Open
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 ex…
View article: Galactic evolution of copper in the light of NLTE computations
Galactic evolution of copper in the light of NLTE computations Open
We have developed a model atom for Cu with which we perform statistical\nequilibrium computations that allow us to compute the line formation of Cu I\nlines in stellar atmospheres without assuming Local Thermodynamic Equilibrium\n(LTE). We…
View article: TOPoS: III. An ultra iron-poor CEMP multiple system
TOPoS: III. An ultra iron-poor CEMP multiple system Open
Aims. One of the primary objectives of the TOPoS survey is to search for the most metal-poor stars. Our search has led to the discovery of one of the most iron-poor objects known, SDSS J092912.32+023817.0. This object is a multiple system,…
View article: HST/STIS abundances in the uranium rich metal poor star CS 31082-001: Constraints on the r-Process
HST/STIS abundances in the uranium rich metal poor star CS 31082-001: Constraints on the r-Process Open
International audience
View article: The O-Na And Mg-Al Anticorrelations In Turn-Off And Early Subgiants In Globular Clusters
The O-Na And Mg-Al Anticorrelations In Turn-Off And Early Subgiants In Globular Clusters Open
High dispersion spectra (R greater than or similar to 40 000) for a quite large number of stars at the main sequence turn-off and at the base of the giant branch in NGC 6397 and NGC 6752 were obtained with the UVES on Kueyen (VLT UT2). The…
View article: Chemical abundance analysis of 19 barium stars
Chemical abundance analysis of 19 barium stars Open
International audience
View article: HIGH-RESOLUTION ABUNDANCE ANALYSIS OF VERY METAL-POOR R-I STARS
HIGH-RESOLUTION ABUNDANCE ANALYSIS OF VERY METAL-POOR R-I STARS Open
Context. Moderately r-process-enriched stars (r-I; +0.3 ≤ [Eu/Fe] ≤ +1.0) are at least four times as common as those that are greatly enriched in r-process elements (r-II; [Eu/Fe] > +1.0), and the abundances in their atmospheres are import…
View article: The first generations of stars
The first generations of stars Open
View article: Lithium abundance in a turnoff halo star on an extreme orbit
Lithium abundance in a turnoff halo star on an extreme orbit Open
The lithium abundance in turnoff stars of the old population of our Galaxy is\nremarkably constant in the metallicity interval -2.8\\textless{}[Fe/H]\n\\textless{}-2.0, defining a plateau. The Li abundance of these turnoff stars is\nclearl…
View article: High-resolution abundance analysis of HD 140283
High-resolution abundance analysis of HD 140283 Open
HD 140283 is a reference subgiant that is metal poor and confirmed to be a very old star. The abundances of this type of old star can constrain the nature and nucleosynthesis processes that occurred in its (even older) progenitors. The pre…
View article: Grid of theoretical NLTE equivalent widths of four Ba ii lines and barium abundance in cool stars
Grid of theoretical NLTE equivalent widths of four Ba ii lines and barium abundance in cool stars Open
We present a grid of computed non-local thermodynamic equilibrium (NLTE)\nequivalent widths (EW) and NLTE abundance corrections for four Ba II lines:\n4554, 5853, 6141, and 6496 A. The grid can be useful in deriving the NLTE\nbarium abunda…
View article: TOPoS
TOPoS Open
In the course of the TOPoS (Turn Off Primordial Stars) survey, aimed at discovering the lowest metallicity stars, we have found several carbon-enhanced metal-poor (CEMP) stars. We here present our analysis of six CEMP stars. Calcium and ca…