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Abundance gradients and their variations constitute one of the main constraints of chemical evolution models for the Galaxy. The time evolution of the gradients, in particular, is essential to distinguish between models involving different physical processes and time scales (see for example [6] and [8]). The gradients can be derived from different types of objects, but the study of their time variation requires the use of objects with a reasonably large age span, such as planetary nebulae (PN) and open clusters. In the present work, we compare the results obtained from PN with recent determinations from open clusters and cepheid variable stars. These objects offer some additional advantages compared with PN, such as more accurate distances and ages.

We discuss recent observational evidence illustrating the current limitations plaguing classical LTE abundance analyses of cool ( < 5500 K), chromospherically active stars. Although significant progress on this issue can be evidently expected from a more realistic atmospheric modelling and treatment of NLTE line formation, a homogeneous abundance study of a large sample of K-type stars may also prove valuable in disentangling temperature and activity effects.

We present here the results of abundance measurements of iron, calcium and nickel in four open clusters, from UVES spectra of solar–type stars. A code developed by one of the authors (François) performs line recognization, equivalent width measurements and finally obtains the abundances by means of OSMARCS LTE model atmosphere [4]. Temperature, gravity and microturbulence velocity have to be input to the program. This is made in an automatic way for a grid of values chosen on photometric basis. Those that best reproduce excitation and ionization equilibria are selected and used, namely when no significant trend of the computed abundances is seen, neither versus the excitation potential of the line nor versus its equivalent width, and for which the abundances obtained with lines of different ionization stages of the same specie give equal results within the errors. This check is made with iron lines, we have in fact at least thirty Fe I lines in each star, and six Fe II lines.

We are determining light- and heavy-element abundance ratios in a variety of standard stars of spectral types A through K by comparing their observed highresolution echelle spectra to spectra calculated over broad wavelength regions. These calculations extend from 3740Å to 9000Å in all stars, and include the mid-ultraviolet for those stars with echelle spectra from the Hubble Space Telescope. We report on progress to date in comparing our calculations line-by-line to the observed spectra.

We use intermediate resolution ( ~ 19 300) spectroscopic observations in the spectral region including the Li 6708Å line to study 341 stars in the star forming region (SFR) NGC6530. Based on the optical color-magnitude diagrams (CMD), they are G, K and early M type pre-main sequence (PMS) cluster candidates. 72% of them are probable cluster members since are X-ray sources detected in a Chandra-ACIS observation ([2]). We use our spectroscopic measurements to confirm cluster membership by means of radial velocities and to investigate the Li abundance of cluster members.

Coronal abundances have been a subject of debate in the last years due to the availability of high-quality X-ray spectra of many cool stars. Coronal abundance determinations have generally been compared to solar photospheric abundances; from this a number of general properties have been inferred, such as the presence of a coronal metal depletion with an inverse First Ionization Potential dependence, with a functional form dependent on the activity level. We report a detailed analysis of the coronal abundance of 4 stars with various levels of activity and with accurately known photospheric abundances. The coronal abundance is determined using a line flux analysis and a full determination of the differential emission measure. We show that, when coronal abundances are compared with real photospheric values for the individual stars, the resulting pattern can be very different; some active stars with apparent Metal Abundance Deficiency in the corona have coronal abundances that are actually consistent with their photospheric counterparts.

To understand the chemical evolution of galaxies, we need a deep understanding of the evolution of massive stars and their role in processing and delivering chemical elements. B-type supergiants represent a substantial population in this context. We present here initial results from non-LTE, line-blanketed stellar atmosphere modelling [1] of a large sample of B0-B5 supergiants (see Fig.1). We focus in this report on revisions to the effective temperature scales, finding reasonable agreement with the temperatures of [2] for B1-B5 supergiants. For early type supergiants (B0-B1), the less luminous Ib’s are hotter than Ia’s as expected (excluding HD190603 (B1.5 Ia+) which is a hypergiant). The temperature discrepancy between B0 Ia’s & B0 Ib’s is up to 2500 K, decreasing to 1000 K for B0.5 and remains as 1000 K or less for later B type supergiants. Whilst some early B type supergiants are slightly cooler compared to the Humphreys et al. temperatures [2], a few B0.5 Ia & Ib stars appear to be slightly hotter. This discrepancy requires further investigation, since recent OB supergiant revised temperature scales have shown a trend for temperatures to be slightly cooler [3] than previously thought from [2].

In an effort to determine accurate stellar parameters and abundances for a large sample of nearby stars, we have performed the detailed analysis of 350 highresolution spectra of FGK dwarfs and giants. This sample will be used to investigate behavior of chemical elements and kinematics in the thick and thin disks, in order to better constrain models of chemical and dynamical evolution of the Galaxy.

The most recently discovered Galactic component – thick disk – still needs high-resolution spectral investigations since its origin and evolution is not understood enough. Elemental abundance ratios in the metallicity range −0.68 ≤ [Fe/H] ≤ −0.10 were determined in a sample of 10 thick-disk dwarfs and compared with results of other stars investigated as well as with models of thin disk chemical evolution.

We present abundance results from our Keck/HIRES observations of giants in the Galactic Bulge. We confirm that the metallicity distribution of giants in the lowreddening bulge field Baade’s Window can be well-fit by a closed-box enrichment model. We also confirm previous observations that find enhanced [Mg/Fe], [Si/Fe] and [Ca/Fe] for all bulge giants, including those at super-solar metallicities. However, we find that the [O/Fe] ratios of metal-rich bulge dwarfs decrease with increasing metallicity.