University of Heidelberg

Δμ - binaries

The duplicity of a 'Δμ - binary' is indicated by a statistically significant difference Δμ between the quasi-instantaneously measured HIPPARCOS proper motion and a long-term averaged, mean proper motion. The HIPPARCOS proper motion is taken from the HIPPARCOS Catalogue.
The mean proper motion is usually either taken directly from a ground-based astrometric catalogue (after having applied appropriate systematic corrections), or a new mean proper motion (μ0) is calculated from the ground-based position(s) and the HIPPARCOS position. The following catalogues have been used for obtaining mean proper motions:
FK5 (Basic fundamental stars) (Veröff.Astron.Rechen-Inst. No.32), FK5 extension (Veröff.Astron.Rechen-Inst. No.33), FK5 Supplement (Veröff.Astron.Rechen-Inst. No.34), GC (Boss' General Catalogue [1937]), and Tycho-2 proper motions [2000].

Up to now, we have checked more than 90 000 HIPPARCOS stars for Δμ duplicity. The resulting Δμ binaries, about 7000 in total, are given in the following finding list for various samples of stars:

Δμ binaries found in the HIPPARCOS Catalogue

The basic principles of the method are explained in the paper: Wielen, R., Dettbarn, C., Jahreiß, H., Lenhardt, H., Schwan, H.: Indications on the binary nature of individual stars derived from a comparison of their HIPPARCOS proper motions with ground-based data. I. Basic principles, Astron. Astrophys. 346, 675-685 (1999).

Contact: C. Dettbarn
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