9.3.6 Hipparcos-2
Original catalogue:
—ftp://cdsarc.u-strasbg.fr/pub/cats/I/311/
A new reduction of the astrometric data as produced by the Hipparcos mission has been published, claiming accuracies for nearly all stars brighter than magnitude Hp = 8 to be better, by up to a factor 4, than in the original catalogue.
The formal errors on the parallaxes for the new catalogue are confirmed. The presence of a small amount of additional noise, though unlikely, cannot be ruled out.
The new reduction of the Hipparcos astrometric data provides an improvement by a factor 2.2 in the total weight compared to the catalogue published in 1997, and provides much improved data for a wide range of studies on stellar luminosities and local galactic kinematics.
Hipparcos-2 contains 117 955 sources.
Cross-match algorithm
According to the definition used in this work, Hipparcos-2 is a sparse catalogue. In the cross-match algorithm Hipparcos-2 is thus the leading catalogue, this means that counterparts for Hipparcos-2 objects are searched for in Gaia. For this catalogue the special treatment to account for the small issues in Gaia astrometry, especially for bright stars, was applied.