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We present the abundance measurements of several elements (Fe, Ca, Na, Ni, Ti, Al, Cr, Si) for 20 solar--type stars belonging to four Galactic open clusters: NGC 3680, IC 4651, Praesepe, and M 67. Oxygen abundances were in addition measured for most of the stars in each cluster apart from IC 4651. For NGC 3680 accurate abundance determinations using high--resolution spectra covering a large spectral domain are computed for the first time. We used UVES high--resolution, high signal to noise ratio spectra and performed a differential analysis with respect to the sun, by measuring equivalent widths and assuming LTE. The most surprising result is a significant supersolar metallicity for Praesepe ([Fe/H]=0.27+-0.10). As for the other clusters, we confirm a supersolar metallicity for IC 4651 ([Fe/H]=0.12+-0.05), a solar metallicity for M 67 ([Fe/H]=0.03+-0.04) and a slight subsolar metallicity for NGC 3680 ([Fe/H]=-0.04+-0.03). We find that the abundance ratios of almost all elements are solar, with the notable exception of oxygen in NGC 3680 and Praesepe, supersolar in the former cluster ([O/Fe]=0.2+-0.05) and as low as [O/Fe]=-0.4+-0.1 in the latter. Observations of several objects per cluster is required to obtain robust results, especially for those elements with a limited number of suitable lines.
We present a CCD photometric survey for the search of variable stars in four open clusters namely Berkeley 69, King 5, King 7, and Berkeley 20. The time series observations were carried out for 1 and/or 2 nights for each of the clusters in the year 1
A Rb deficiency by a factor two with respect to the Sun has been found in M dwarfs of solar metallicity. This deficiency is difficult to understand from both the observational and nucleosynthesis point of views. To test the reliability of this Rb def
Open Clusters have long been used to study the chemo-dynamical evolution of the Galactic disk. This requires an homogeneously analysed sample covering a wide range of ages and distances. In this aper we present the OCCASO second data release. This co
The spatial distribution of elemental abundances in the disc of our Galaxy gives insights both on its assembly process and subsequent evolution, and on the stellar nucleogenesis of the different elements. Gradients can be traced using several types o
We present a detailed near-infrared chemical abundance analysis of 10 red giant members of the Galactic open cluster NGC 752. High-resolution (R$simeq$45000) near-infrared spectral data were gathered with the Immersion Grating Infrared Spectrograph (