THE ASTRONOMICAL JOURNAL    VOLUME 108, NUMBER 3, PAGE 1016      SEPTEMBER 1994

  THE METALLICITIES AND KINEMATICS OF RR LYRAE VARIABLES. I. NEW OBSERVATIONS
                                OF LOCAL STARS

                               ANDREW C. LAYDEN

           Department of Astronomy, Yale University, P.O. Box 208101
                       New Haven, Connecticut 06520-8101
                       Electronic mail: alayden@noao.edu


                                   ABSTRACT
    
    In order to study the structure and formation history of the galaxy, we
    have obtained low-to-moderate dispersion spectra of 302 nearby RR Lyrae
    variables of Bailey type "ab."  We derived abundances, typically
    accurate to 0.15-0.20 dex and calibrated to the Zinn & West [ApJS, 55,
    45 (1984)] globular cluster metallicity scale, from the pseudo-
    equivalent widths of the Ca II K, Hdelta, Hgamma, and Hbeta lines.
    Radial velocities accurate to between 2 and 30 km/s were obtained from
    the spectra and from the literature.  Distances accurate to between 5%
    and 20% were derived from published apparent magnitudes and Burstein &
    Heiles [AJ, 87, 1165 (1982)] reddenings.  The metallicity distribution
    of the RR Lyrae stars peaks at [Fe/H]_K approx. -1.5, and is narrower
    than that of the Ryan & Norris [AJ, 101, 1865 (1991)] subdwarfs, as
    expected since the most metal-rich and metal-poor progenitors
    preferentially appear as stable red and blue horizontal branch stars,
    rather than as RR Lyrae.  The metal-rich tail of the RR Lyrae
    distribution extends to [Fe/H]_K approx. 0, and a qualitative analysis
    of the distribution of distances from the galactic plane shows that the
    stars in this tail (i.e., [Fe/H]_K > -1.0) are more concentrated to the
    plane than the more metal-poor stars.  The abundance distribution of
    the local RR Lyrae stars is in excellent agreement with the changing
    abundance distributions of distant RR Lyrae stars as a function of
    galactocentric distance, as derived by Suntzeff et al. [ApJ, 367, 528
    (1991)], who ascribed this change to systematic variations in
    horizontal branch morphology (probably age variations) with
    galactocentric distance.  The abundance distribution of the local RR
    Lyrae stars also agrees well with those of the distant RR Lyrae stars
    as a function of distance from the galactic plane.  There is no
    evidence for an abundance gradient in this direction, suggesting that
    gaseous dissipation did not play a major role in the formation of the
    outer halo.