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Paper: Back to the Future: The Calcium HK Survey of Beers, Preston, and Shectman
Volume: 491, Fifty Years of Wide Field Studies in the Southern Hemisphere: Resolved Stellar Populations in the Galactic Bulge and the Magellanic Clouds
Page: 140
Authors: Beers, T. C.
Abstract: In the late 1970s, George Preston and Steve Shectman of the Carnegie Observatories began a novel effort to identify large numbers of candidate metal-poor stars in the Galaxy. By inserting an interference filter into the focal plane of a traditional objective prism plate, they demonstrated the ability to isolate roughly a 200 Å band around the CaII H and K lines, and thereby enabled a deeper objective prism survey (by several magnitudes) than previously possible. This work began with the Curtis Schmidt telescope at CTIO and was continued for more than a decade by Beers on the UM/CTIO Curtis Schmidt telescope and the Burrell Schmidt telescope at KPNO. Medium-resolution spectroscopic observations of HK survey candidates, using the CTIO 4m, CTIO 1.5m, KPNO 4m, KPNO 2.1m, and numerous other telescopes worldwide, greatly enlarged the number of known stars with [Fe/H] < –2.0 dex, and set the stage for the next large survey for metal-poor stars, i.e., the Hamburg/ESO survey of Christlieb and collaborators. After briefly reviewing this history, I highlight examples of the numerous unique objects discovered during the course of the HK survey, including the first extremely metal-poor star with measured U and Th, and other highly r-process-element enhanced stars, the discovery of carbon-enhanced metal-poor stars, and stars used for exploring the apparently complex nature of the halo of the Galaxy. An update on contemporary follow-up of HK survey metal-poor candidates is provided.
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