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Astron. Astrophys. 323, L57-L60 (1997)

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Letter to the Editor

The Tycho Catalogue *

E. Hog 1, G. Bässgen 2, U. Bastian 3, D. Egret 4, C. Fabricius 1, V. Großmann 2, J.L. Halbwachs 4, V.V. Makarov 1, M.A.C. Perryman 5, P. Schwekendiek 3 and K. WagnerA. Wicenec 2, 2

1 Copenhagen University Observatory, Juliane Maries Vej 30, DK-2100 Copenhagen O, Denmark
2 Astronomisches Institut, Waldhäuserstrasse 64, D-72076 Tübingen, Germany
3 Astronomisches Rechen-Institut, Mönchhofstrasse 12-14, D-69120 Heidelberg, Germany
4 Observatoire de Strasbourg, 11 rue de l'Université, F-67000 Strasbourg, France
5 Astrophysics Division, European Space Agency, ESTEC, Noordwijk 2200AG, The Netherlands

Received 29 April 1997 / Accepted 1 May 1997

Abstract

The principal observational characteristics of the Tycho Catalogue, and a summary of its main astrometric and photometric properties, are presented. Median astrometric standard errors (in position, parallax, and annual proper motion) are typically around 7 mas for stars brighter than [FORMULA]  mag, and approximately 25 mas for [FORMULA]  mag, at the catalogue epoch (J1991.25). The Tycho Catalogue was adjusted so that the six global rotation and spin components of the catalogue reference frame coincide with those of the Hipparcos Catalogue. It therefore materialises the ICRS reference system, coinciding with its principal axes at the level of [FORMULA]  mas, and with proper motions consistent with an inertial system at the level of [FORMULA]  mas/yr. The [FORMULA] constituent stars provide a mean sky density of [FORMULA]  stars deg-2. The catalogue and associated epoch photometry annex data are available in machine-readable form as part of the final Hipparcos mission products.

Key words: Tycho – Hipparcos – astrometry – photometry – catalogues

* Based on observations made with the ESA Hipparcos astrometry satellite

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© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998

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