Search Publications
Visual binary orbits and masses POST HIPPARCOS
Söderhjelm, Staffan
The parallaxes from Hipparcos are an important ingredient to derive more accurate masses for known orbital binaries, but in order to exploit the parallaxes fully, the orbital elements have to be known to similar precision. The present work gives improved orbital elements for some 205 systems by combining the Hipparcos astrometry with existing grou…
Fundamental parameters of nearby stars from the comparison with evolutionary calculations: masses, radii and effective temperatures
Allende Prieto, C.; Lambert, D. L.
The Hipparcos mission has made it possible to constrain the positions of nearby field stars in the colour-magnitude diagram with very high accuracy. These positions can be compared with the predictions of stellar evolutionary calculations to provide information on the basic parameters of the stars: masses, radii, effective temperatures, ages, and …
Mapping the contours of the Local bubble: preliminary results
Crifo, F.; Lallement, R.; Welsh, B. Y. +1 more
We present preliminary results from a long-term program of mapping the neutral absorption characteristics of the local interstellar medium, taking advantage of Hipparcos stellar distances. Equivalent widths of the NaI D-line doublet at 5890 Å are presented for the lines-of-sight towards some 143 new target stars lying within 300 pc of the Sun. Usi…
Open clusters with Hipparcos. I. Mean astrometric parameters
Arenou, F.; Robichon, N.; Turon, C. +1 more
New memberships, mean parallaxes and proper motions of all 9 open clusters closer than 300 pc (except the
Revisiting Hipparcos data for pre-main sequence stars
Arenou, F.; Robichon, N.; Bertout, C.
We cross-correlate the Herbig & Bell and Hipparcos Catalogues in order to extract the results for young stellar objects (YSOs). We compare the distances of individual young stars and the distance of their presumably associated molecular clouds, taking into account post-Hipparcos distances to the relevant associations and using Hipparcos interm…
HIPPARCOS distance calibrations for 9 open clusters
van Leeuwen, Floor
Parallaxes have been determined for 9 nearby open clusters in order to derive a composite, age resolved, HR diagram. An age-luminosity relation was found to exist for main-sequence stars. A suggested 1 mas error in the Hipparcos parallax for the Pleiades, to explain the difference with the ground-based photometric distance estimate, seems unlikely…
Barium abundances in cool dwarf stars as a constraint to s- and r-process nucleosynthesis
Bikmaev, I.; Mashonkina, L.; Gehren, T.
We revise barium abundances in 11 cool stars with metallicities ranging from -2.65 to 0.05. The results are based on differential NLTE model atmosphere analyses of spectra that have a typical S/N of 200 and a resolution of 40000 or 60000. To minimize systematic errors of theoretical modeling and to be sure that elemental surface abundances are not…
High-precision VLBI astrometry of radio-emitting stars
Lestrade, J. -F.; Preston, R. A.; Jones, D. L. +5 more
Multiple-epoch phase-referenced VLBI observations of 11 radio-emitting stars have been conducted as part of an astrometric program to link the Hipparcos optical reference frame to the radio extragalactic reference frame. We present the VLBI positions, proper motions and trigonometric parallaxes from this program in the ICRF (International Celestia…
The delta Scuti star FG Virginis. IV. Mode identifications and pulsation modelling
Garrido, R.; Pamyatnykh, A. A.; Breger, M. +1 more
This paper examines the mode identification and presents pulsation models for FG Vir, for which 24 frequencies have been detected. Histograms of the frequency spacings show peaks which are identified with adjacent radial orders and rotational splitting. Pulsational l values are deduced for eight modes by comparing the observed photometric phase la…
Detection of moving groups among early type stars
Figueras, F.; Torra, J.; Chen, B. +1 more
Our procedure to detect moving groups in the solar neighbourhood \cite{chen} in the four-dimensional space of the stellar velocity components and age has been improved. The method, which takes advantadge of non-parametric estimators of density distribution to avoid any a priori knowledge of the kinematic properties of these stellar groups, now inc…