Letter to the Editor
The Tycho-2 catalogue of the 2.5 million brightest stars *
E. Hog 1,
C. Fabricius 1,
V.V. Makarov 1,
S. Urban 2,
T. Corbin 2,
G. Wycoff 2,
U. Bastian 3,
P. Schwekendiek 3 and
A. Wicenec 4
Received 3 January 2000 / Accepted 21 January 2000
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 the star mapper of the ESA Hipparcos satellite, but Tycho-2 is much bigger and slightly more precise, owing to a more advanced reduction technique. Components of double stars with separations down to 0.8 arcsec are included. Proper motions precise to about 2.5 mas/yr are given as derived from a comparison with the Astrographic Catalogue and 143 other ground-based astrometric catalogues, all reduced to the Hipparcos celestial coordinate system. Tycho-2 supersedes in most applications Tycho-1, as well as the ACT and TRC catalogues based on Tycho-1.
Key words: astrometry stars: fundamental parameters catalogs
* Based on observations made with the ESA Hipparcos astrometry satellite. The catalogue is distributed on CD-ROM and through the astronomical data centres, and further information is given on the website http://www.astro.ku.dk/~erik/Tycho-2 .
This article contains no SIMBAD objects.
© European Southern Observatory (ESO) 2000
Online publication: March 9, 2000