Astronomisches Rechen-Institut Heidelberg

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ARI-Heidelberg Veröffentlichungen, No. 39

Author(s): Wielen, R., Schwan, H., Dettbarn, C., Lenhardt, H., Jahreiß, H., Jährling, R., Khalisi, E.
Title: Astrometric Catalogue TYC2 + HIP. Derived from a Combination of the HIPPARCOS Catalogue with the Proper Motions given in the TYCHO-2 Catalogue.
Source: Veröffentlichungen Astronomisches Rechen-Institut Heidelberg, No. 39, Verlag G. Braun, Karlsruhe, 36 pages
ISBN: 3-7650-0538-X
ISSN: 0373-7055
Year: 2001
Abstract: The TYC2+HIP Catalogue is a suitable combination of the results of the HIPPARCOS astrometry satellite with ground-based data summarized in the TYCHO-2 Catalogue (Høg et al. 2000). The TYC2+HIP contains 89908 stars with direct solutions. Such direct solutions are appropriate for single stars or for objects which can be treated like single stars. From the 89908 stars with direct solutions in the TYC2+HIP we have selected 72943 objects as "astrometrically excellent stars", since their instantaneous proper motions and mean (time-averaged) ones do not differ significantly. Hence most of the astrometrically excellent stars are well-behaving "single-star candidates" with good astrometric data. These stars are most suited for high-precision astrometry. On the other hand, 2793 of the stars in the TYC2+HIP are Δμ binaries in the sense of Wielen et al. (1999). Many of them are newly discovered probable binaries with no other hitherto known indication of binarity. The TYC2+HIP gives, besides the classical "single-star mode" solutions (SI mode), other solutions which take into account the fact that hidden astrometric binaries among "apparently single-stars" introduce sizable "cosmic errors" into the quasi-instantaneously measured HIPPARCOS proper motions and positions. The TYC2+HIP gives in addition to the SI mode the "long-term prediction (LTP) mode" and the "short-term prediction (STP) mode". These LTP and STP modes are on average the most precise solutions for apparently single stars, depending on the epoch difference with respect to the HIPPARCOS epoch of about 1991. The typical mean error of a TYC2+HIP proper motion in the single-star mode is 0.83 mas/year. This is about a factor of 1.3 better than the typical HIPPARCOS errors for these stars of 1.08 mas/year. In the long-term prediction mode, in which cosmic errors are taken into account, the TYC2+HIP proper motions have a typical mean error of 1.06 mas/year, which is by a factor 1.8 better than the corresponding error for the HIPPARCOS values of 1.86 mas/year (cosmic errors included).
Preprint issued: December 2001

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Letzte Änderung/Updated: 14.10.2002