Astronomisches Rechen-Institut Heidelberg

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Preprint No. 88

Author(s): Jahreiß, H., Wielen, R., Fuchs, B.
Title: The Impact of HIPPARCOS on Our Knowledge of Nearby Stars
Source: In: Brosche, P., Dick, W.R., Schwarz, O., Wielen, R. (eds.): The message of the angles - astrometry from 1798 to 1998. Proc. AG Spring Meeting, Gotha, 11-15 May 1998, Acta Hist. Astron. 3; Harri Deutsch, Frankfurt, 171-180
Year: 1998
Abstract: The astrometric satellite Hipparcos observed almost 90% of the presently known nearby stars in the magnitude range accessible by the satellite. It detected almost 200 new nearby objects, the nearest one at 5.4 pc, and 39 new components. Consequently, the new version of the Catalogue of Nearby Stars (CNS4), which was compiled on the basis of the Hipparcos measurements, achieved an unprecedent quality. Compared with the last ground-based version (CNS3) the number of stars within the chosen distance limit of 25 pc remained more or less the same. But, a considerable shift to larger distances took place, so, that a high portion of stars formerly included due to large and rather poor trigonometric parallaxes could now be removed, unequivocally. The bright part (absolute V-magnitude brighter than 9 mag) of the new nearby star sample is complete within a much larger volume than before. In other words, Hipparcos cleaned up the bright portion of the CM diagram, which represents now the true distribution of the massive stars within 25 pc and allows more precise studies of kinematics, metallicity and age effects. This is supported by the Hipparcos Survey which allows an extension of the distance limit to 50 pc for the brightest stars without any loss of completeness. Likewise, the bright end of local stellar luminosity function could be determined with higher accuracy than before: the result is a 15 per cent decrease in star number density, and in a slightly lower stellar mass density of 0.039 solar masses pro cubic parsec.
Preprint issued: August 1998

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