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Paper: The Horizontal Branch Morphology of Halo Field Stars
Volume: 92, Formation of the Galactic Halo. . . . Inside and Out
Page: 36
Authors: Kinman, T. D.; Allen, Christine
Abstract: A blue, variable and red part of the horizontal branch (HB) can be identified in globular clusters, but only the variable component (RR Lyrae stars) and part of the blue horizontal branch (BHB) can be identified in the field. Our knowledge of these two HB components (RR Lyrae stars and BHB stars with \bv >=-0.02) in the solar neighbourhood is discussed. Both these local BHB stars and the halo RR Lyrae stars have similar galactic rotation and orbital properties and so they genuinely belong to the halo and not to the thick-disk. Current estimates of the local space densities of these stars are lower limits because of the uncertainty about the completeness of the samples. Other properties of the local HB stars (orbital characteristics and the mean period of the type ab RR Lyrae stars) are discussed together with what is known of the HB morphology of the stars in the North Galactic Polar fields.
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