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The Tycho-2 catalogue of the 2.5 million brightest stars
Makarov, V. V.; Bastian, U.; Fabricius, C. +6 more
The Tycho-2 Catalogue presented here is an astrometric reference catalogue containing positions and proper motions as well as two-colour photometric data for the 2.5 million brightest stars in the sky. The Tycho-2 positions and magnitudes are based on precisely the same observations as the original Tycho Catalogue (hereafter Tycho-1) collected by …
Revision of the initial-to-final mass relation
Weidemann, V.
The initial-to final mass relation is revised in view of new theoretical and observational data. Recent stellar evolution models predict core masses at the beginning of the thermally pulsing asymptotic giant branch which practically coincide with final white dwarf masses derived for NGC 3532 and the binary white dwarf PG 0922+162. The Hyades white…
The Nature of the lithium rich giants. Mixing episodes on the RGB and early-AGB
Charbonnel, C.; Balachandran, S. C.
We present a critical analysis of the nature of the so-called Li-rich RGB stars. For a majority of the stars, we have used Hipparcos parallaxes to determine masses and evolutionary states by comparing their position on the Hertzsprung-Russell diagram with theoretical evolutionary tracks. Among the twenty Li-rich giants whose location on the HR dia…
Construction and verification of the Tycho-2 Catalogue
Makarov, V. V.; Bastian, U.; Fabricius, C. +6 more
The construction of the Tycho-2 Catalogue is described. The catalogue contains astrometric positions and proper motions as well as two-colour photometric data for 2.5 million stars. The Tycho-2 positions and magnitudes are based on precisely the same observations as the original Tycho Catalogue (hereafter Tycho-1) collected by the sky mapper of th…
Exploring the brown dwarf desert with Hipparcos
Queloz, D.; Arenou, F.; Udry, S. +2 more
The orbital elements of 11 spectroscopic binaries with brown dwarf candidates (M2 sin i between 0.01 and 0.08 Msun) are combined with the Hipparcos observations in order to derive astrometric orbits. Estimations of the masses of the secondary components are thus calculated. It appears that 5 secondary masses are more than 2 s…
A proper motion study of the globular cluster ω Centauri
Freeman, K. C.; van Leeuwen, F.; Le Poole, R. S. +2 more
A proper motion study is presented of the globular cluster ω Centauri. Based on 100 plates obtained with the Yale-Columbia 66 cm (26 inch) refractor, and ranging in epoch from 1931 till 1935 and 1978 till 1983, differential proper motions are obtained for 9847 stars. The limiting magnitude (photographic) is 16.0 for the centre of the cluster, 16.5…
Mass-radius relations for white dwarf stars of different internal compositions
Althaus, L. G.; Panei, J. A.; Benvenuto, O. G.
The purpose of this work is to present accurate and detailed mass-radius relations for white dwarf (WD) models with helium, carbon, oxygen, silicon and iron cores, and with and without a hydrogen envelope, by using a fully updated stellar evolutionary code. We considered masses from 0.15 Msun to 0.5 Msun for the case of hel…
Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Makarov, V. V.; Fabricius, C.
Using observations obtained with the Tycho instrument of the ESA Hipparcos satellite, a two-colour photometry is produced for components of more than 7 000 Hipparcos double and multiple stars with angular separations 0.1 to 2.5 arcsec. We publish 9473 components of 5173 systems with separations above 0.3 arcsec. The majority of them did not have T…
Kinematics of young stars. I. Local irregularities
Figueras, F.; Torra, J.; Fernández, D.
The local velocity field of young stars is dominated by the galactic rotation, the kinematics of the Gould Belt and the nearest OB associations and open clusters, and the kinematics of the spiral structure. We re-examined here this local velocity field by using a large sample of nearby O and B stars from the Hipparcos Catalogue. The high quality a…
A high-resolution study of episodic mass loss from the carbon star TT Cygni
Eriksson, K.; Gustafsson, B.; Olofsson, H. +3 more
CO radio line observations with the IRAM Plateau de Bure interferometer show that the carbon star TT Cyg is surrounded by a large (radius ~ 35arcsec or 2.7x1017 cm), geometrically thin (average width ~ 2farcs 5 or 1.9x1016 cm) shell of gas, which has a remarkable overall spherical symmetry (e.g., its radius varies by less tha…