Absolute Magnitudes and Kinematics of RR Lyrae Stars via Statistical Parallax

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Session 32 -- Galaxy Dynamics
Display presentation, Tuesday, 31, 1994, 9:20-6:30

[32.02] Absolute Magnitudes and Kinematics of RR Lyrae Stars via Statistical Parallax

A.C.Layden (CTIO), R.B.Hanson (UCO/Lick Observatory), S.L.Hawley (Michigan State University)

The absolute magnitude of the RR Lyrae stars is integral in determining the distances to the old stellar systems in our Galaxy and to other Local Group galaxies, and in determining the ages of the Galactic globular clusters. We present new estimates of the RR Lyrae star absolute magnitude as a function of metal abundance, based on a new set of statistical parallax solutions. This analysis is an improvement over previous works for several reasons: (1) it relies mainly on new absolute proper motions from the Lick Northern Proper Motion Survey, which are of uniformly high quality. (2) new metal abundances and radial velocities are employed; the former are of particularly high quality and uniformity. (3) the improved metallicities, combined with kinematic analyses, allow us for the first time to properly separate thick--disk and halo stars; these populations must be treated separately for the solutions to be valid, and (4) over 200 stars are used in this analysis ($>$20\% have thick disk kinematics), significantly more than in previous solutions. We discuss the kinematic properties of the local RR Lyrae stars, and briefly discuss our absolute magnitude results with regard to the distances and ages of some RR Lyrae-bearing populations.

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