Stellar Populations and Variable Stars in the Core of the Globular Cluster M5

Abstract

We report the discovery of a variable blue straggler in the core of the globular cluster M5, based on a 12-hour long series of images obtained with the Planetary Camera aboard the Hubble Space Telescope. In addition, we present the light curves of 28 previously unknown or poorly studied large-amplitude variable stars (all but one are RR Lyrae) in the cluster core. A (V, U-I) color-magnitude diagram shows 24 blue stragglers within 2 core radii of the cluster center. The blue straggler population is significantly more centrally concentrated than the horizontal branch and red giant stars.

22 pages, 18 postscript figures, 1 postscript table, AJ, in press (Feb 1998)

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• Variable Stars in the Globular Cluster M5. Application of the Image Subtraction Method
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• RR Lyrae stars and the horizontal branch of NGC 5904 (M5)
• SX Phoenicis Stars in the Core of 47 Tucanae
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