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A HIPPARCOS Census of the Nearby OB Associations
Brown, A. G. A.; de Bruijne, J. H. J.; de Zeeuw, P. T. +2 more
A comprehensive census of the stellar content of the OB associations within 1 kpc from the Sun is presented, based on Hipparcos positions, proper motions, and parallaxes. It is a key part of a long-term project to study the formation, structure, and evolution of nearby young stellar groups and related star-forming regions. OB associations are unbo…
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…
Stellar Iron Abundances: Non-LTE Effects
Thévenin, F.; Idiart, T. P.
We report new statistical equilibrium calculations for Fe I and Fe II in the atmosphere of late-type stars. We used atomic models for Fe I and Fe II having, respectively, 256 and 190 levels, as well as 2117 and 3443 radiative transitions. Photoionization cross sections are from the Iron Project. These atomic models were used to investigate non-LTE…
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 …
The ROSAT all-sky survey catalogue of the nearby stars
Schmitt, J. H. M. M.; Sterzik, M. F.; Voges, W. +1 more
We present X-ray data for all entries of the Third Catalogue of Nearby Stars \cite[(Gliese & Jahreiss 1991)]{gli91} that have been detected as X-ray sources in the ROSAT all-sky survey. The catalogue contains 1252 entries yielding an average detection rate of 32.9 percent. In addition to count rates, source detection parameters, hardness ratio…
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
Radii and Effective Temperatures for G, K, and M Giants and Supergiants
Kulkarni, S. R.; Palmer, D.; van Belle, G. T. +13 more
Interferometrically determined angular diameters obtained at the Palomar Testbed Interferometer (PTI) for 69 giant and supergiant stars are presented. Spectral types of the 59 giant stars generally lie between G6 and M6, although a B7 giant is included; the nine bright giants and supergiants have spectral types between F5 and M5. Comparison of the…
The Age of β Pictoris
Barrado y Navascués, David; Stauffer, John R.; Song, Inseok +1 more
We have reanalyzed data for the proposed moving group associated with β Pictoris in order to determine if the group (or part of it) is real and, if so, to derive an improved age estimate for β Pic. By using new, more accurate proper motions from PPM and Hipparcos and a few new radial velocities, we conclude that on kinematic grounds, most of the p…
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…