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The Tycho-Gaia Astrometric Solution

Published online by Cambridge University Press:  07 March 2018

Lennart Lindegren Open the ORCID record for Lennart Lindegren [Opens in a new window]
Lennart Lindegren*
Affiliation:
Lund Observatory, Department of Astronomy and Theoretical Physics Lund University, Box 43, SE-22100 Lund, Sweden email: lennart@astro.lu.se
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Abstract

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Gaia DR1 is based on the first 14 months of Gaia's observations. This is not long enough to reliably disentangle the parallax effect from proper motion. For most sources, therefore, only positions and magnitudes are given. Parallaxes and proper motions were nevertheless obtained for about two million of the brighter stars through the Tycho-Gaia astrometric solution (TGAS), combining the Gaia observations with the much earlier Hipparcos and Tycho-2 positions. In this review I focus on some important characteristics and limitations of TGAS, in particular the reference frame, astrometric uncertainties, correlations, and systematic errors.

Keywords

Catalogsastrometryreference systemsstars: distancesstars: general

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