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The Open Cluster M67 as a Fundamental Standard of Reference for Stellar Properties

Published online by Cambridge University Press:  04 August 2017

Kenneth Janes
Kenneth Janes*
Affiliation:
Boston University

Abstract

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With the possible exception of the Hyades, M67 is the best-studied star cluster. Accurate photoelectric photometry exists well down onto the main sequence and proper motion studies have isolated cluster stars from the field. From photometry and spectroscopy, its composition is determined to be almost exactly the same as the Sun, with an age about one-half billion years less. This similarity to the Sun permits an accurate determination of distance to M67 independently of other distance measurements. Using the Sun as a reference, the distance modulus of M67 is found to be 9.48 mag. An extensive analysis of possible sources of error leads to an uncertainty (standard error) of ± 0.15 mag., with the chief sources of error being the color index of the Sun, the composition of the cluster, and its age. The M67 distance uncertainty compares favorably with Hanson's (1975) Hyades modulus of 3.29 ± 0.08.

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 111: Calibration of Fundamental Stellar Quantities , 1985 , pp. 361 - 364
Copyright
Copyright © Reidel 1985 

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