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Overview of the lithium problem in metal-poor stars and new results on 6Li
Roger Cayrel, Matthias Steffen, Piercarlo Bonifacio +2
Two problems are discussed here. The first one is the 0.4 dex discrepancy between the 7Li abundance derived from the spectra of metal-poor halo stars on the one hand, and from Big…
The photospheric solar oxygen project: I. Abundance analysis of atomic lines and influence of atmospheric models
Elisabetta Caffau, Hans-G. Ludwig, Matthias Steffen +5
The solar oxygen abundance has undergone a major downward revision in the last decade, the most noticeable one being the update including 3D hydrodynamical simulations to model the…
NLTE determination of the aluminium abundance in a homogeneous sample of extremely metal-poor stars
S. M. Andrievsky, M. Spite, S. A. Korotin +5
Aims: Aluminium is a key element to constrain the models of the chemical enrichment and the yields of the first supernovae. But obtaining precise Al abundances in extremely metal-p…
The ESO Large Programme First Stars
P. Bonifacio, J. Andersen, S. Andrievsky +19
In ESO period 65 (April-September 2000) the large programme 165.N-0276, led by Roger Cayrel, began making use of UVES at the Kueyen VLT telescope. Known within the Team and outside…
First Stars XI. Chemical composition of the extremely metal-poor dwarfs in the binary CS 22876--032
J. I. González Hernández, P. Bonifacio, H. -G. Ludwig +15
We have used high-resolution, high-S/N ratio spectra from the UVES spectrograph at the ESO VLT telescope. Long-term radial-velocity measurements and broad-band photometry allow us…
First Stars VIII -- Enrichment of the neutron-capture elements in the early Galaxy
P. Francois, E. Depagne, V. Hill +12
Our aim is to measure accurate, homogeneous neutron-capture element abundances for the sample of 32 EMP giant stars studied earlier in this series, including 22 stars with [Fe/H] $…
Line shift, line asymmetry, and the 6Li/7Li isotopic ratio determination
Roger Cayrel, Matthias Steffen, Hum Chand +6
Context: Line asymmetries are generated by convective Doppler shifts in stellar atmospheres, especially in metal-poor stars, where convective motions penetrate to higher atmospheri…
NLTE determination of the sodium abundance in a homogeneous sample of extremely metal-poor stars
S. M. Andrievsky, M. Spite, S. A. Korotin +5
Abundance ratios in extremely metal-poor (EMP) stars are a good indication of the chemical composition of the gas in the earliest phases of the Galaxy evolution. It had been found…
First stars VII. Lithium in extremely metal poor dwarfs
P. Bonifacio, P. Molaro, T. Sivarani +12
Aims. This study aims to determine the level and constancy of the Spite plateau as definitively as possible from homogeneous high-quality VLT-UVES spectra of 19 of the most metal-p…
First stars X. The nature of three unevolved Carbon-Enhanced Metal-Poor stars
T. Sivarani, T. C. Beers, P. Bonifacio +13
From high-resolution VLT/UVES spectra (R~43,000), we determine abundances or upper limits for Li, C, N, O, and other important elements, as well as 12C/13C isotopic ratio for three…
First stars IX -Mixing in extremely metal-poor giants. Variation of the 12C/13C, [Na/Mg] and [Al/Mg] ratios
M. Spite, R. Cayrel, V. Hill +11
Extremely metal-poor (EMP) stars preserve a fossil record of the composition of the ISM when the Galaxy formed. It is crucial, however, to verify whether internal mixing has modifi…
The chemical evolution of Barium and Europium in the Milky Way
G. Cescutti, P. Francois, F. Matteucci +2
We compute the evolution of the abundances of barium and europium in the Milky Way and we compare our results with the observed abundances from the recent UVES Large Program "First…
Lead abundance in the uranium star CS 31082-001
B. Plez, V. Hill, R. Cayrel +6
In a previous paper we were able to measure the abundance of uranium and thorium in the very-metal poor halo giant BPS CS 31082-001, but only obtained an upper limit for the abunda…
New analysis of the two carbon-rich stars CS 22948-27 and CS 29497-34 : binarity and neutron-capture elements
B. Barbuy, M. Spite, F. Spite +4
We have carried out a new determination of abundances in the very metal-poor CH/CN strong stars CS 29497-34 and CS 22948-27, using high-resolution spectra obtained with the HARPS s…
First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements
M. Spite, R. Cayrel, B. Plez +11
We have investigated the poorly-understood origin of nitrogen in the early Galaxy by determining N abundances in 35 extremely metal-poor halo giants (22 stars have [Fe/H]<-3.0) usi…
The evolution of the Milky Way from its earliest phases : constraints on stellar nucleosynthesis
Patrick Francois, Francesca Matteucci, Roger Cayrel +3
We computed the evolution of the abundances of O, Mg, Si, Ca, K, Ti, Sc, Ni, Mn, Co, Fe and Zn in the Milky Way. We made use of the most widely adopted nucleosynthesis calculations…
First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
R. Cayrel, E. Depagne, M. Spite +11
In the framework of an ESO Large Programme high quality spectra of 70 very metal-poor dwarfs and giants were obtained with the VLT-UVES combination. This paper reports the detailed…
First stars IV.CS 29497-030: Evidence for operation of the s-process at very low metallicity
T. Sivarani, P. Bonifacio, P. Molaro +12
We present an abundance analysis of the very metal-poor, carbon-enhanced star CS 29497-030. Our results indicate that this unusually hot turnoff star (Teff = 6650K, log g = 3.5) ha…
Elemental abundances of metal poor carbon rich lead star: CS29497-030
T. Sivarani, P. Bonifacio, P. Molaro +12
We present here the abundance analysis of a metal poor carbon rich lead star, CS29497-030. High resolution and high signal to noise spectra were obtained using the UVES spectrograp…
First Stars II. Elemental abundances in the extremely metal-poor star CS 22949--037: A diagnostic of early massive supernovae
E. Depagne, V. Hill, M. Spite +10
CS 22949--037 is one of the most metal-poor giants known ([Fe/H]), and it exhibits large overabundances of carbon and nitrogen (Norris et al.). Using VLT-UVES spectra…
The extreme r-element rich, iron-poor halo giant CS31082-001: Implications for the r-process site(s) and radioactive cosmochronology
V. Hill, B. Plez, R. Cayrel +10
We present a high-resolution spectroscopic analysis of the bright (V=11.7), extreme halo giant CS31082-001 ([Fe/H] = -2.9), obtained in an ESO-VLT Large Programme dedicated to very…
Measurement of stellar age from uranium decay
R. Cayrel, V. Hill, T. Beers +10
The ages of the oldest stars in the Galaxy indicate when star formation began, and provide a minimum age for the Universe. Radioactive dating of meteoritic material and stars relie…
R-process pattern in the Very-Metal-Poor Halo Star CS31082-001
V. Hill, B. Plez, R. Cayrel +1
The very-metal-poor halo star CS31082-001 was discovered to be very strongly r-process-enhanced during the course of a VLT+UVES high-resolution follow-up of metal-poor stars identi…
First Measurement of Uranium/Thorium ratio in a very old Star: Implications for the age of the Galaxy
R. Cayrel
During an ESO-VLT large program devoted to high-resolution spectroscopy of extremely metal-poor stars selected from the H&K survey of Beers and colleagues, a [Fe/H] giant star was…