Search Publications
The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics
Holmberg, J.; Nordström, B.; Andersen, J.
Context: Ages, chemical compositions, velocity vectors, and Galactic orbits for stars in the solar neighbourhood are fundamental test data for models of Galactic evolution. The Geneva-Copenhagen Survey of the Solar Neighbourhood (Nordström et al. 2004; GCS), a magnitude-complete, kinematically unbiased sample of 16 682 nearby F and G dwarfs, is th…
Parallaxes and proper motions for 20 open clusters as based on the new Hipparcos catalogue
van Leeuwen, F.
Context: A new reduction of the astrometric data as produced by the Hipparcos mission has been published, claiming that the accuracies for nearly all stars brighter than magnitude Hp = 8 are improved, by up to a factor 4, compared to the original catalogue. As correlations between the underlying abscissa residuals have also been reduced by more th…
The interstellar Ca II distance scale
Krełowski, J.; Galazutdinov, G. A.; Strobel, A. +1 more
Aims: We attempt to extend the relation between the strengths of the interstellar Ca II lines and the distances to early-type stars to objects beyond 1 kiloparsec, with the line saturation taken into account.
Methods: We measure the Ca II K and Ca II H equivalent widths, and compute Ca II column densities for 262 lines of sight towards early-t…
Lithium abundances of halo dwarfs based on excitation temperature. I. Local thermodynamic equilibrium
García Pérez, A. E.; Norris, J. E.; Ryan, S. G. +2 more
Context: The discovery of the Spite plateau in the abundances of 7Li for metal-poor stars led to the determination of an observationally deduced primordial lithium abundance. However, after the success of the Wilkinson Microwave Anisotropy Probe (WMAP) in determining the baryon density, Ω_Bh2, there was a discrepancy between …
A spectroscopic survey of the youngest field stars in the solar neighbourhood. I. The optically bright sample
Motch, C.; Freire Ferrero, R.; Bouvier, J. +8 more
Aims: We present the first results of an ambitious ground-based observation programme conducted on 1-4 m class telescopes. Our sample consists of 1097 active and presumably young stars, all of them being optical (Tycho Catalogue) counterparts of ROSAT All-Sky Survey X-ray sources in the northern hemisphere. In this paper, we concentrate on the opt…
Accurate fundamental parameters of CoRoT asteroseismic targets. The solar-like stars HD 49933, HD 175726, HD 181420, and HD 181906
Bruntt, H.
Context: The CoRoT satellite has provided high-quality light curves of several solar-like stars. Analysis of these light curves provides oscillation frequencies that make it possible to probe the interior of the stars. However, additional constraints on the fundamental parameters of the stars are important for the theoretical modelling to be succe…
Planetary companions around the K giant stars 11 Ursae Minoris and HD 32518
Guenther, E. W.; Pasquini, L.; Hatzes, A. P. +2 more
Context: 11 UMi and HD 32518 belong to a sample of 62 K giant stars that has been observed since February 2004 using the 2m Alfred Jensch telescope of the Thüringer Landessternwarte (TLS) to measure precise radial velocities (RVs).
Aims: The aim of this survey is to investigate the dependence of planet formation on the mass of the host star by…
The chemical composition of carbon stars. The R-type stars
Abia, C.; Cristallo, S.; Plez, B. +2 more
Aims. The aim of this work is to shed some light on the problem of the formation of carbon stars of R-type from a detailed study of their chemical composition.
Methods: We use high-resolution and high signal-to-noise optical spectra of 23 R-type stars (both early- and late-types) selected from the Hipparcos catalogue. The chemical analysis is …
A systematic study of variability among OB-stars based on HIPPARCOS photometry
Lefèvre, L.; Moffat, A. F. J.; Marchenko, S. V. +1 more
Context: Variability is a key factor for understanding the nature of the most massive stars, the OB stars. Such stars lie closest to the unstable upper limit of star formation.
Aims: In terms of statistics, the data from the HIPPARCOS satellite are unique because of time coverage and uniformity. They are ideal to study variability in this larg…
[O I] sub-arcsecond study of a microjet from an intermediate mass young star: RY Tauri
Dougados, C.; Cabrit, S.; Ferruit, P. +2 more
Context: High-resolution studies of microjets in T Tauri stars (cTTs) reveal key information on the jet collimation and launching mechanism, but only a handful of systems have been mapped so far.
Aims: We wish to perform a detailed study of the microjet from the 2 M⊙ young star RY Tau, to investigate the influence of its higher stel…