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Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| Absolute stellar proper motions with reference to galaxies of the M81 group
We report on the measurement of absolute proper motions of stars ofmagnitude 7 to 14.5 in a 2 deg X 2 deg field in the region of the M81group of galaxies. This work is part of the Bonn program for theextragalactic link of Hipparcos. The proper motions were determined froma collection of photographic plates covering the time interval from 1894to 1994. The absolute reference system for the proper motions isrepresented by the galaxies M81, M81, and NGC3077, for which accurateoptical reference positions were obtained by means of an imagecross-correlation technique. For the majority of stars, the internalproper motion accuracy is better than 1 mas/a. The precision of therealization of the absolute system is found to be around 1 mas/a. Intotal, our measurements yield absolute proper motions for 24 Hipparcosstars and positions, proper motions and photometry for 330 additionalstars including a number of visual binaries and high proper motionstars. Among the latter one G-type sub-dwarf is identified. The resultsare relevant as a contribution to the Hipparcos link, but also as adatabase for kinematic investigations.
| Observations of double stars and new pairs. XIV
Results of a continuing survey of visual double stars are presented,including 4880 measurements made from February 1987 to November 1989.The positions in WDS format and Durchmusterung numbers are given for 194pairs first reported here. Micrometer measurements of 1142 doubles madewith the Swarthmore 61 cm refractor are presented. Magnitudes areestimated for some of the objects. Plate measurements, plateorientations, position angles, number of nights, and measured exposuresare given. Visual observations of 342 pairs obtained in May 1989 atCerro Tololo, mostly with the 1.0 m reflector, are reported.
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