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Description
A new reduction of the astrometric data as produced by the Hipparcos mission has been published, claiming accuracies for nearly all stars brighter than Hipparcos magnitude H_p = 8 to be better, by up to a factor 4, than in the original catalog. The new Hipparcos astrometric catalog has been checked for the quality of the data and the consistency of the formal errors as well as the possible presence of error correlations. The differences with the earlier publication of the Hipparcos Catalog are explained in the reference paper. The internal errors are followed through the reduction process, and the external errors are investigated on the basis of a comparison with radio observations of a small selection of stars, and the distribution of negative parallaxes. Error correlation levels are investigated and the reduction by more than a factor 10 as obtained in the new catalog is explained. The formal errors on the parallaxes for the new catalog 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 Hipparcos catalog published in 1997, and, according to the author, provides much improved data for a wide range of studies on stellar luminosities and local galactic kinematics. Note that this catalog version is slightly different from the one published in the book, as an error that sometimes affected the goodness of fit value for the solution was corrected. The first version of these data archived at the CDS (between June and 15 September 2008) also contained errors which were corrected after this date. This table was created by the HEASARC in August 2009 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/I/311">CDS Catalog I/311</a> file hip2.dat, "the Astrometric Catalogue". This is a service provided by NASA HEASARC .
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