The Pleiades, Map-based Trigonometric Parallaxes of Open Clusters. V.

The Multichannel Astrometric Photometer and Thaw Refractor (Thaw/MAP) of the University of Pittsburgh's Allegheny Observatory have been used to determine the trigonometric parallax of the Pleiades star cluster. The parallax determined, 000764 with a standard error of ±000043 (corresponding to a distance modulus of 5.59 ± 0.12 mag) places the cluster significantly further away than indicated by the mean parallax of cluster members drawn from the Hipparcos catalog. The distance derived here is in general agreement with values based on main-sequence fitting, indicating that cluster members are not subluminous as suggested by the Hipparcos-based results. The current study combines the data from our initial study of this cluster with new observations of that region and of a second Pleiades region in an overlapping configuration. It thus supersedes our first determination of the parallax of the Pleiades cluster. A third Pleiades field is being selected for future measurement of the cluster's trigonometric parallax, and assistance with the luminosity classification of reference stars is sought.

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