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Paper: Open Cluster Distances from Hipparcos parallaxes
Volume: 167, Harmonizing Cosmic Distance Scales in a Post-Hipparcos Era
Page: 52
Authors: van Leeuwen, Floor
Abstract: An overview is presented of Hipparcos parallax determinations for open clusters. The reliability of these determinations is considered in a discussion about the size and scale of local systematic correlations in the Hipparcos parallax errors. Localized correlations between Hipparcos parallax errors are found to be at a level of at most 0.1~mas, disappearing beyond separations of 1.2deg. There is no sign of significant large scale distortions. Formal errors as found for the cluster parallaxes are therefore a realistic reflection of their true accuracy. A composite HR diagram for the 10 nearest open clusters confirms this, by showing systematic behaviour as a function of cluster age similar to, but much more pronounced than, what can be observed from theoretical isochrones.
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