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The Problem of HIPPARCOS Distances to Open Clusters. II. Constraints from Nearby Field Stars
This paper examines the discrepancy between distances to nearby openclusters as determined by parallaxes from Hipparcos compared totraditional main-sequence fitting. The biggest difference is seen forthe Pleiades, and our hypothesis is that if the Hipparcos distance tothe Pleiades is correct, then similar subluminous zero-age main-sequence(ZAMS) stars should exist elsewhere, including in the immediate solarneighborhood. We examine a color-magnitude diagram of very young andnearby solar-type stars and show that none of them lie below thetraditional ZAMS, despite the fact that the Hipparcos Pleiades parallaxwould place its members 0.3 mag below that ZAMS. We also presentanalyses and observations of solar-type stars that do lie below theZAMS, and we show that they are subluminous because of low metallicityand that they have the kinematics of old stars.
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Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Avci |
| Sað Açýklýk: | 05h22m42.72s |
| Yükselim: | +13°13'44.7" |
| Görünürdeki Parlaklýk: | 9.135 |
| Uzaklýk: | 48.685 parsek |
| özdevim Sað Açýklýk: | 14.5 |
| özdevim Yükselim: | -45.3 |
| B-T magnitude: | 10.108 |
| V-T magnitude: | 9.216 |
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