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The O-Na and Mg-Al anticorrelations in turn-off and early subgiants in globular clusters
Pasquini, L.; Bonifacio, P.; Grundahl, F. +16 more
High dispersion spectra (R>~ 40 000) for a quite large number of stars at the main sequence turn-off and at the base of the giant branch in NGC 6397 and NGC 6752 were obtained with the UVES on Kueyen (VLT UT2). The [Fe/H] values we found are -2.03+/- 0.02+/- 0.04\ and -1.42+/- 0.02+/- 0.04\ for NGC 6397 and NGC 6752 respectively, where the firs…
delta Scuti and related stars: Analysis of the R00 Catalogue
Rodríguez, E.; Breger, M.
We present a comprehensive analysis of the properties of the pulsating delta Scuti and related variables based mainly on the content of the recently published catalogue by Rodríguez et al. (\cite{retal00a}, hereafter R00). In particular, the primary observational properties such as visual amplitude, period and visual magnitude and the contribution…
Order and chaos in the local disc stellar kinematics induced by the Galactic bar
Fux, R.
The Galactic bar causes a characteristic splitting of the disc phase space into regular and chaotic orbit regions which is shown to play an important role in shaping the stellar velocity distribution in the Solar neighbourhood. A detailed orbital analysis within an analytical 2D rotating barred potential reveals that this splitting is mainly dicta…
A Hipparcos study of the Hyades open cluster. Improved colour-absolute magnitude and Hertzsprung-Russell diagrams
de Bruijne, J. H. J.; de Zeeuw, P. T.; Hoogerwerf, R.
Hipparcos parallaxes fix distances to individual stars in the Hyades cluster with an accuracy of ~ 6 percent. We use the Hipparcos proper motions, which have a larger relative precision than the trigonometric parallaxes, to derive ~ 3 times more precise distance estimates, by assuming that all members share the same space motion. An investigation …
The solar neighbourhood age-metallicity relation - Does it exist?
Holmberg, J.; Feltzing, S.; Hurley, J. R.
We derive stellar ages, from evolutionary tracks, and metallicities, from Strömgren photometry, for a sample of 5828 dwarf and sub-dwarf stars from the Hipparcos Catalogue. This stellar disk sample is used to investigate the age-metallicity diagram in the solar neighbourhood. Such diagrams are often used to derive a so called age-metallicity relat…
Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups
Montes, D.; López-Santiago, J.; Fernández-Figueroa, M. J. +1 more
We present here high resolution echelle spectra taken during three observing runs of 14 single late-type stars identified in our previous studies (Montes et al. \cite{M_etal01b}, hereafter Paper I) as possible members of different young stellar kinematic groups (Local Association (20-150 Myr), Ursa Major group (300 Myr), Hyades supercluster (600 M…
The effective temperatures of carbon-rich stars
Bergeat, J.; Knapik, A.; Rutily, B.
We evaluate effective temperatures of 390 carbon-rich stars. The interstellar extinction on their lines of sights was determined and circumstellar contributions derived. The intrinsic (dereddened) spectral energy distributions (SEDs) are classified into 14 photometric groups (HCi, CVj and SCV with i=0,5 and j=1,7). The new sc…
On OH line formation and oxygen abundances in metal-poor stars
Asplund, M.; García Pérez, A. E.
The formation of the UV OH spectral lines has been investigated for a range of stellar parameters in the light of 3D hydrodynamical model atmospheres. The low atmospheric temperatures encountered at low metallicities compared with the radiative equilibrium values enforced in classical 1D hydrostatic model atmospheres have a profound impact on the …
Stellar encounters with the solar system
Lestrade, J. -F.; Latham, D. W.; Paredes, J. M. +5 more
We continue our search, based on Hipparcos data, for stars which have encountered or will encounter the solar system (García-Sánchez et al. \cite{Garcia}). Hipparcos parallax and proper motion data are combined with ground-based radial velocity measurements to obtain the trajectories of stars relative to the solar system. We have integrated all tr…
Lithium abundances for 185 main-sequence stars: Galactic evolution and stellar depletion of lithium
Zhao, G.; Nissen, P. E.; Chen, Y. Q. +1 more
We present a survey of lithium abundances in 185 main-sequence field stars with 5600 <~ Teff <~ 6600 K and -1.4 <~ [Fe/H] <~ +0.2 based on new measurements of the equivalent width of the lambda 6708 Li I line in high-resolution spectra of 130 stars and a reanalysis of data for 55 stars from Lambert et al. (\cite{Lambert91}).…