相关论文: A super-Li rich turnoff star in NGC 6397 - the puz…

We report on the discovery of a super-Li rich turn-off star in the old (12 Gyr), metal poor ([Fe/H]=-2.1 dex) globular cluster (GC) NGC 6397, based on high-resolution MIKE/Magellan spectra. This star shows an unusually high lithium…

The Li-rich turn-off star in the globular cluster NGC 6397 could represent the smoking gun for some very rare episode of Li enrichment in globular clusters. We aim to understand the nature of the Li enrichment by performing a spectroscopic…

We make use of high resolution, high signal-to-noise ratio spectra of 12 turn-off stars in the metal-poor globular cluster NGC 6397 to measure its lithium content. We conclude that they all have the same lithium abundance A(Li) = 2.34 with…

Most Globular Clusters are believed to host a single stellar populations. They can thus be considered a good place to study the Spite plateau and probe for possible evolutionary modifications of the Li content. We want to determine the Li…

To alleviate the discrepancy between the prediction of the primordial lithium abundance in the universe and the abundances observed in Pop II dwarfs and subgiant stars, it has been suggested that the stars observable today have undergone…

We present the chemical composition of the bright companion to the millisecond pulsar J1740-5340 in NGC 6397, based on high resolution spectra. Though the large rotation velocity of the star broadens the lines and complicates the analysis,…

VLT-UVES high resolution spectra of seven turnoff stars in the metal-poor globular cluster NGC 6397 have been obtained. Atmospheric parameters and abundances of several elements (Li, Na, Mg, Ca, Sc, Ti, Cr, Fe, Ni, Zn and Ba) were derived…

The "stellar" solution to the cosmological lithium problem proposes that surface depletion of lithium in low-mass, metal-poor stars can reconcile the lower abundances found for Galactic halo stars with the primordial prediction. Globular…

We present FLAMES/GIRAFFE spectroscopy obtained at the Very Large Telescope (VLT). Using these observations we have been able for the first time to observe the Li I doublet in the Main Sequence stars of a Globular Cluster. We also observed…

The lithium abundance in turnoff stars of the old population of our Galaxy is remarkably constant in the metallicity interval -2.8\textless{}[Fe/H] \textless{}-2.0, defining a plateau. The Li abundance of these turnoff stars is clearly…

Thanks to the high multiplex and efficiency of Giraffe at the VLT we have been able for the first time to observe the Li I doublet in the Main Sequence (MS) stars of a Globular Cluster. At the same time we observed Li in a sample of…

We have analyzed high-dispersion spectra in the Li 6708 Angstrom region for 167 stars within the anticenter cluster, NGC 2204. From 105 probable members, abundance analysis of 45 evolved stars produces [Fe/H] = -0.40 +/- 0.12, [Si/Fe] =…

We aim to determine abundances of Li, O and Na in a sample of of 110 turn-off (TO) stars, in order to study the evolution of light elements in this cluster and to put our results in perspective with observations of other globular and open…

We present high resolution observations (FWHM=15 km/sec) of the Li region in 5 stars belonging to the old (14 Gyrs), metal rich ([Fe/H]=-0.7) globular cluster 47Tuc. At the ESO NTT telescope we obtained EMMI spectra for three V about 17.4…

We measure the nitrogen abundance in 5 Turn Off(TO) stars of the Globular Clusters NGC 6397 and NGC 6752, and compare the cluster abundances with those of field stars of comparable metallicity. We determine the nitrogen abundance from the…

Li abundances for 9 Turnoff (TO) stars of the intermediate metallicity cluster ([Fe/H]=-1.4) NGC6752 are presented. The cluster is known to show abundance anomalies and anticorrelations observed in both evolved and main sequence stars. We…

We present chemical abundances in three red giants and two turn-off stars in the metal poor Galactic globular cluster (GC) NGC 6397 based on spectroscopy obtained with the MIKE high resolution spectrograph on the Magellan 6.5-m Clay…

I use literature data and a new temperature calibration to determine the Li abundances in the globular cluster M 92. Based on the same data, Boesgaard et al. have claimed that there is a dispersion in Li abundances in excess of…

{The aim of this work is to investigate the relations between the abundances of different elements in the globular cluster M4, selected for its uniform deficiency of iron, to explore the best models explaining the pattern of these observed…

We present a homogeneous photometric and spectroscopic analysis of 18 stars along the evolutionary sequence of the metal-poor globular cluster NGC 6397 ([Fe/H] = -2), from the main-sequence turnoff point to red giants below the bump. The…