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Revisiting Eggen’s Moving Groups

Presentation #332.02 in the session “Variable Stars II”.

Published onJun 18, 2021
Revisiting Eggen’s Moving Groups

In his series of papers spanning from 1958 to 1998, Olin Eggen proposed and discussed the idea of moving groups of stars scattered across the sky that were formed from dissolved open clusters. By using the astrometric data available at the time and assuming the members of the moving group shared a common space motion, Eggen extended the classic convergent point analysis to these moving groups. He could then determine the distance modulus to each star in the group and could apply all the tools used to study open clusters to these scattered groups of stars. While the concept of moving groups is still considered useful by many astronomers, it was nevertheless controversial from the onset at least in part because of the limited accuracy of the astrometric data then available. Since Eggen’s death in 1998, substantially more accurate astrometric data has become available with the launch of the Hipparcos and Gaia spacecrafts. In addition, the volume and quality of spectroscopic and photometric data has grown enormously since Eggen started his project. In this presentation we will outline a proposal to revisit Eggen’s moving groups, starting with some of the groups whose reality have been most often challenged.

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