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The Li/Li isotopic ratio in the metal-poor binary CS22876--032
J. I. González Hernández, P. Bonifacio, E. Caffau +4
We present high-resolution and high-quality UVES spectroscopic data of the metal-poor double-lined spectroscopic binary CS 22876--032 ([Fe/H] dex), with the goal to der…
TOPoS V: Abundance ratios in a sample of very metal-poor turn-off stars
P. François, E. Caffau, P. Bonifacio +12
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 sta…
Using the CIFIST grid of CO5BOLD 3D model atmospheres to study the effects of stellar granulation on photometric colours. II. The role of convection accross the H-R diagram
A. Kučinskas, J. Klevas, H. -G. Ludwig +3
We studied the influence of convection on the spectral energy distributions, photometric magnitudes, and colour indices of different types of stars across the H-R diagram. The 3D h…
TOPoS: IV. Chemical abundances from high-resolution observations of seven EMP stars
P. Bonifacio, E. Caffau, M. Spite +15
Extremely metal-poor stars provide us with indirect information on the first generations of massive stars. The TOPoS survey has been designed to increase the census of these stars…
Using the CIFIST grid of CO5BOLD 3D model atmospheres to study the effects of stellar granulation on photometric colours. I. Grids of 3D corrections in the UBVRI, 2MASS, Hipparcos, Gaia, and SDSS systems
P. Bonifacio, E. Caffau, H. -G. Ludwig +9
The atmospheres of cool stars are temporally and spatially inhomogeneous due to the effects of convection.The influence of this inhomogeneity, referred to as granulation, on colour…
The photospheric solar oxygen project: IV. 3D-NLTE investigation of the 777 nm triplet lines
M. Steffen, D. Prakapavičius, E. Caffau +5
The solar photospheric oxygen abundance is still widely debated. Adopting the solar chemical composition based on the "low" oxygen abundance, as determined with the use of three-di…
High-resolution abundance analysis of very metal-poor r-I stars
C. Siqueira-Mello, V. Hill, B. Barbuy +9
Moderately r-process-enriched stars (r-I) are at least four times as common as those that are greatly enriched in r-process elements (r-II), and the abundances in their atmospheres…
TOPoS: I. Survey design and analysis of the first sample
E. Caffau, P. Bonifacio, L. Sbordone +14
The metal-weak tail of the metallicity distribution function (MDF) of the Galactic Halo stars contains crucial information on the formation mode of the first generation of stars. T…
Oxygen spectral line synthesis: 3D non-LTE with CO5BOLD hydrodynamical model atmospheres
D. Prakapavicius, M. Steffen, A. Kucinskas +4
In this work we present first results of our current project aimed at combining the 3D hydrodynamical stellar atmosphere approach with non-LTE (NLTE) spectral line synthesis for a…
First stars XVI. STIS/HST abundances of heavy-elements in the uranium-rich star CS 31082-001
C. Siqueira Mello, M. Spite, B. Barbuy +14
Detailed abundances of the elements produced by r-process nucleosynthesis in various circumstances are our best observational clues to their origin, since the site(s) of r-element…
6Li detection in metal-poor stars: can 3D model atmospheres solve the second lithium problem?
M. Steffen, R. Cayrel, E. Caffau +3
The presence of 6Li in the atmospheres of metal-poor halo stars is usually inferred from the detection of a subtle extra depression in the red wing of the 7Li doublet line at 670.8…
NLTE determination of the calcium abundance and 3D corrections in extremely metal-poor stars
Monique Spite, S. M. Andrievsky, F. Spite +6
(Abridged) Extremely metal-poor stars contain the fossil records of the chemical composition of the early Galaxy. The NLTE profiles of the calcium lines were computed in a sample o…
NLTE strontium abundance in a sample of extremely metal poor stars and the Sr/Ba ratio in the early Galaxy
S. M. Andrievsky, F. Spite, S. A. Korotin +5
Heavy element abundances in extremely metal-poor stars provide strong constraints on the processes of forming these elements in the first stars. We attempt to determine precise abu…
Extremely metal-poor stars in SDSS fields
Piercarlo Bonifacio, Elisabetta Caffau, Patrick François +12
Some insight on the first generation of stars can be obtained from the chemical composition of their direct descendants, extremely metal-poor stars (EMP), with metallicity less tha…
First stars XIII. Two extremely metal-poor RR Lyrae stars?
C. J. Hansen, B. Nordstroem, P. Bonifacio +11
The chemical composition of extremely metal-poor stars (EMP stars; [Fe/H]<~ -3) is a unique tracer of early nucleosynthesis in the Galaxy. As such stars are rare, we wish to find c…
First Stars XIV. Sulfur abundances in extremely metal-poor (EMP) stars
Monique Spite, E. Caffau, S. M. Andrievsky +15
Sulfur is important: the site of its formation is uncertain, and at very low metallicity the trend of [S/Fe] against [Fe/H] is controversial. Below [Fe/H]=-2.0, [S/Fe] remains cons…
Convection and 6Li in the atmospheres of metal-poor halo stars
M. Steffen, R. Cayrel, P. Bonifacio +2
Based on 3D hydrodynamical model atmospheres computed with the CO5BOLD code and 3D non-LTE (NLTE) line formation calculations, we study the effect of the convection-induced line as…
Solar abundances and 3D model atmospheres
H. -G. Ludwig, E. Caffau, M. Steffen +3
We present solar photospheric abundances for 12 elements from optical and near-infrared spectroscopy. The abundance analysis was conducted employing 3D hydrodynamical (CO5BOLD) as…
6Li in metal-poor halo stars: real or spurious?
M. Steffen, R. Cayrel, P. Bonifacio +2
The presence of convective motions in the atmospheres of metal-poor halo stars leads to systematic asymmetries of the emergent spectral line profiles. Since such line asymmetries a…