A Δμ binary is an object that has a statistcally signifcant difference between instantaneous proper motion (as measured by HIPPARCOS) and a longer-term proper motion as indicated by longer-term observations.
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:
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 (see source metadatum).
The stars listed here are those investigated (ca. 90000) with one (or more) F-measures exceeding 3.44.
We list many newly detected binaries, but also ones already known from other data, e.g. visual ones. In many cases of already known binaries, the F values should be considered as qualitative 'flags' for binarity only, since the proper motions compared may not refer to the same 'reference point' (e.g., HIPPARCOS refers to component A, while the FK5 to the center-of-mass).
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