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In this paper we present an homogeneous analysis of photospheric abundances based on high-resolution spectroscopy of a sample of 182 barium stars and candidates. We determined atmospheric parameters, spectroscopic distances, stellar masses, ages, luminosities and scale height, radial velocities, abundances of the Na, Al, $alpha$-elements, iron-peak elements, and s-process elements Y, Zr, La, Ce, and Nd. We employed the local-thermodynamic-equilibrium model atmospheres of Kurucz and the spectral analysis code {\sc moog}. We found that the metallicities, the temperatures and the surface gravities for barium stars can not be represented by a single gaussian distribution. The abundances of $alpha$-elements and iron peak elements are similar to those of field giants with the same metallicity. Sodium presents some degree of enrichment in more evolved stars that could be attributed to the NeNa cycle. As expected, the barium stars show overabundance of the elements created by the s-process. By measuring the mean heavy-element abundance pattern as given by the ratio [s/Fe], we found that the barium stars present several degrees of enrichment. We also obtained the [hs/ls] ratio by measuring the photospheric abundances of the Ba-peak and the Zr-peak elements. Our results indicated that the [s/Fe] and the [hs/ls] ratios are strongly anti-correlated with the metallicity. Our kinematical analysis showed that 90% of the barium stars belong to the thin disk population. Based on their luminosities, none of the barium stars are luminous enough to be an AGB star, nor to become self-enriched in the s-process elements. Finally, we determined that the barium stars also follow an age-metallicity relation., Comment: 30 pages, 26 figures, 18 tables, accepted for publication in MNRAS

High-velocity halo stars provide important information about the properties of the extreme Galactic halo. The study of unbound and bound Population II stars permits us to better estimate the mass of the halo.} {We carried out a detailed spectroscopic and kinematic study and have significantly refined the distance and the evolutionary state of the star. Its atmospheric parameters, chemical abundances and kinematical properties were determined using high-resolution optical spectroscopy and employing the local-thermodynamic-equilibrium model atmospheres of Kurucz and the spectral analysis code {\sc moog}. We found that CD-62$\degr$1346 is a metal-poor ([Fe/H]=$-$1.7) evolved giant star with $T_{\rm eff}=5300$ K and $\log g=1.7$. The star exhibits high carbon and s-element abundances typical of CH stars. It is also a lead star. Our kinematic analysis of its 3D space motions shows that this star has a highly eccentric ($e=0.91$) retrograde orbit with an apogalactic distance of $\sim 100$ kpc, exceeding by a factor of three the distance to the Magellanic Clouds. The star travels with very high velocity relative to the Galactocentric reference frame ($V_{\rm GRF}=570$ km\,s$^{-1}$). CD-62$\degr$1346 is an evolved giant star and not a subgiant star, as was considered earlier. Whether it is bound or unbound to the Galaxy depends on the assumed mass and on the adopted Galactic potential. We also show that the star HD 5223 is another example of a high-velocity CH star that exceeds the Galactic escape velocity. Possible origins of these two high-velocity stars are briefly discussed. CD-62$\degr$1346 and HD 5223 are the first red giant stars to join the restricted group of hypervelocity stars., Comment: Accepted for publication in Astronomy and Astrophysics

We determined the atmospheric parameters and abundance pattern for a sample of metal-rich barium stars. We used high-resolution optical spectroscopy. Atmospheric parameters and abundances were determined using the local thermodynamic equilibrium atmosphere models of Kurucz and the spectral analysis code MOOG. We show that the stars have enhancement factors, [s/Fe], from 0.25 to 1.16. Their abundance pattern of the Na, Al, alpha-elements, and iron group elements as well as their kinematical properties are similar to the characteristics of the other metal-rich and super metal-rich stars already analyzed. We conclude that metal-rich barium stars do not belong to the bulge population. We also show that metal-rich barium stars are useful targets for probing the s-process enrichment in high-metallicity environments., Comment: 21 pages, 9 figures, accepted for publication in in Astronomy and Astrophysics

The main objective of this work is to investigate the role played by Lower Centaurus Crux (LCC) and Upper Centaurus Lupus (UCL), both subcomponents of the Scorpio Centaurus OB association (Sco-Cen), in the formation of the groups beta Pictoris, TW Hydrae and the eta Chamaeleontis cluster. The dynamical evolution of all the stellar groups involved and of the bubbles and shells blown by LCC and UCL are calculated and followed from the past to the present. This leads to a formation scenario in which (1) the groups beta Pictoris, TW Hydrae were formed in the wake of the shells created by LCC and UCL, (2) the young cluster eta Chamaeleontis was born as a consequence of the collision of the shells of LCC and UCL, and (3) the formation of Upper Scorpius (US), the other main subcomponent of the Sco-Cen association, may have been started by the same process that created eta Chamaeleontis.

The dynamical evolution of the recently detected stellar group Mamajek 2 is studied by means of its past 3D orbit. The past orbits of the open clusters NGC 2516 and $\alpha$ Persei, belonging to the so-called "Local Association", were also computed in order to check for a possible common past dynamical evolution of these systems. To complete the data of the Mamajek 2 small group, we have obtained high resolution FEROS spectra to measure the radial and also the projected rotational velocities of its members; an estimate of its metallicity was obtained as well. Two exceptionally low rotating A-type stars turned out to be a strong magnetic Ap star in one case, and a normal A0 star with near-solar metallicity in the other. The dynamical results showed that NGC 2516 and Mamajek 2 may have had a common origin at the age of 135 $\pm$ 5 Myr. This dynamical age confirms the individual ages of 140 Myr for NGC 2516 and 120 $\pm$ 25 Myr for Mamajek 2 obtained independently by photometric methods. Both these groups appear to have the same solar metallicity giving support to a common birth scenario. The dynamical approach is showing that some bound open clusters can form in a coeval fashion with unbound stellar groups or with associations.

AB Dor is the nearest identified moving group. As with other such groups, the age is important for understanding of several key questions. It is important, for example, in establishing the origin of the group and also in comparative studies of the properties of planetary systems, eventually surrounding some of the AB Dor group members, with those existing in other groups. For AB Dor two rather different estimates for its age have been proposed: a first one, of the order of 50 Myr, by Zuckerman and coworkers from a comparison with Tucana/Horologium moving group and a second one of about 100-125 Myr by Luhman and coworkers from color-magnitude diagrams (CMD). Using this last value and the closeness in velocity space of AB Dor and the Pleiades galactic cluster, Luhman and coworkers suggested coevality for these systems. Because strictly speaking such a closeness does not still guarantee coevality, here we address this problem by computing and comparing the full 3D orbits of AB Dor, Pleiades, alpha Persei and IC 2602. The latter two open clusters have estimated ages of about 85-90 Myr and 50 Myr. The resulting age 119 $\pm$ 20 Myr is consistent with AB Dor and Pleiades being coeval. Our solution and the scenario of open cluster formation proposed by Kroupa and collaborators suggest that the AB Dor moving group may be identified with the expanding subpopulation (Group I) present in this scenario. We also discuss other related aspects as iron and lithium abundances, eventual stellar mass segregation during the formation of the systems and possible fraction of debris discs in AB Dor group., Comment: 11 pages, 5 figures and 2 tables

We derive single-epoch radial velocities for a sample of 56 B-type stars members of the subgroups Upper Scorpius, Upper Centaurus Lupus and Lower Centaurus Crux of the nearby Sco-Cen OB association. The radial velocity measurements were obtained by means of high-resolution echelle spectra via analysis of individual lines. The internal accuracy obtained in the measurements is estimated to be typically 2-3 km/s, but depends on the projected rotational velocity of the target. Radial velocity measurements taken for 2-3 epochs for the targets HD120307, HD142990 and HD139365 are variable and confirm that they are spectroscopic binaries, as previously identified in the literature. Spectral lines from two stellar components are resolved in the observed spectra of target stars HD133242, HD133955 and HD143018, identifying them as spectroscopic binaries., Comment: accepted for publication in A&A

Using Galactic dynamics we have determined the age of the low mass post-T Tauri stars TW Hya Association (TWA). To do so we applied the method of Ortega et al.(2002, 2004) to five stars of the association with Hipparcos measured distances (TWA 1, TWA 4,TWA 9,TWA 11,TWA 19).The method is based on the calculation of the past 3D orbits of the stars. Of these stars only TWA 9 presents a quite different orbit so that it does not appear to be a dynamical member of TWA. The four remaining stars have a first maximum orbits' confinement at the age of -8.3 $\pm{0.8}$ Myr which is considered the dynamical age of TWA. This confinement fixes the probable 3D forming region of TWA with a mean radius of 14.5 pc. This region is related to the older subgroups of the Sco-Cen OB association, Lower Centaurus Crux (LCC) and Upper Centaurus Lupus (UCL), both with a mean age of about 18 Myr. This dynamical age of TWA and that of the $\beta$ Pic Moving Group (BPMG) with an age of 11 Myr, also discussed here, introduce a more precise temporal scale for studies of disks evolution and planetary formation around some stars of these associations. Using the retraced orbit of the runaway star HIP 82868 we examine the possibility that the formation of TWA was triggered by a supernova (SN) explosion. It is shown that for the four considered TWA stars, the expansion in volume is a factor of five since their origin to the present state. This is mainly due to the presently more distant star TWA 19., Comment: Accepted to Astronomical Journal

The results of the complex study of galactic open cluster Trumpler 2 are presented. In order to obtain the proper motions the positions of 2600 stars up to the limit magnitude B ~ 16.25 mag in the area 80x80 arcmin around the cluster were measured on 6 plates with the maximal epoch difference of 63 years. The root-mean error of the relative proper motions is 4.2 mas/yr. The catalogue of BV magnitudes of all the stars in the investigated area was compiled. Astrometric selection of the cluster members within the region of R<16 arcmin from the center of the cluster was made by means of the W.Sanders method. In that field 192 stars were found to have the individual membership probability greater then 85%, 148 of them are situated within the +/-3sigma_(B-V) band around the main sequence of the cluster. They are considered to be cluster members by two criteria. The U-B ~ B-V diagram plotted for the astrometrical cluster members by the data taken from the Washington catalogue of the UBV photometry in the galactic cluster fields (Hoag et al.1961) made it possible to redefine the value of the color excess E(B-V)=0.40 mag. The superposition of the MS of the cluster with the ZAMS Schmidt-Kaler leads to the coincidence at the value of the apparent distance module (V-Mv)=10.50 which corresponds to the distance r=725 pc. The luminosity and mass functions of the Trumpler 2 were constructed and the value of the slope Gamma=-1.90+/-0.22 was determined. The cluster age of 8.913x10^7 yr was determined. It is shown that the red giant on the late stage of the evolution (st N.1095) belongs to cluster and indicates the brightness variability. The possibility that the number of both known and recently discovered variables are cluster members was considered. Tables 2,3,3A,5 will be only available in the electronic form., Comment: 14 pages, 7 figures

The results of astrometric and photometric investigations of the open cluster NGC 7243 are presented. Proper motions of 2165 stars with root-mean-square error of 1.1 mas/yr were obtained by means of PDS scanning of astrometric plates covering the time interval of 97 years. A total of 211 cluster members down to V=15.5 mag have been identified. V and B magnitudes have been determined for 2118 and 2110 stars respectively. Estimations of mass (348Mo < M < 522Mo), age (t=2.5x10^8 yr), distance (r=698 pc) and reddening (E(B-V)=0.24) of the cluster NGC 7243 have been made., Comment: 24 pages, 15 figures. Submitted to Astronomy and Astrophysics

The results of astrometric and photometric investigations of the poorly studied open cluster NGC 1513 are presented. The proper motions of 353 stars with the root-mean-square error of 1.9 mas/yr were obtained by means of the automated measuring complex "Fantasy" scanning of 8 astrometric plates covering the time interval of 101 years. A total of 141 astrometric cluster members have been identified. BV CCD-photometry was made for the stars in a square size 17 arcmin x 17 arcmin centered on cluster. 33 stars with the high reliability were considered to be cluster members by two criteria. The estimation of NGC 1513 age is 2.54 E+08 years. Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/., Comment: 11 pages, 5 figures

Since the eighties we have begun, in Brazil, a search for Post-T Tauri stars. Here we describe the main steps of this research that resulted in the discovery of the nearby TW Hya and Horologium associations. A very recent survey resulted in the detection of three different kinematical groups: 1) the Great Austral Young Association, which is a very extended complex region involving the Horologium and Tucana associations, 2) a CrA extend association and 3) a new group in Pisces., Comment: latex file, 5 pages, no figures, conference: Young Stars Near Eart: Progress and Prospects, ASP Conference Series ed:Ray Jayawardhana and Thomas Greene