Double star data in the Hipparcos Catalogue

The Hipparcos Catalogue contains astrometric results for 117 955 catalogue entries, many of which are in reality double or multiple stars. For 17 917 entries special solutions were made in order to cope with the various manifestations of multiplicity, and 6763 other entries were flagged as suspected binaries but solved as single stars. Details of the special solutions are contained in the Hipparcos Catalogue Double and Multiple Systems Annex, divided in five parts according to the type of solution: resolved systems (13 211 entries with a total of 24 588 components), astrometric binaries with curved proper motion (2622 entries) or orbital solutions (235 entries), 'variability-induced movers' (288 entries) and 'stochastic' solutions (1561 entries). Trigonometric parallaxes and the positions and proper motions in the extragalactic reference system ICRS are provided for all entries.