THE ASTRONOMICAL JOURNAL    VOLUME 107, NUMBER 3, PAGE 1577          APRIL 1994

      REDDENING ESTIMATION FOR HALO RED GIANTS USING uvby PHOTOMETRY

                 BARBARA J. ANTHONY-TWAROG AND BRUCE A. TWAROG

          Department of Physics and Astronomy, University of Kansas,
                          Lawrence, Kansas 66045-2151
                Electronic mail: anthony@kuphsx.phsx.ukans.edu

                                   ABSTRACT

    Updated uvby observations for a larger sample of metal-deficient red
    giants are presented and combined with a select sample of data from the
    literature transformed to a common system.  Using the reddening maps of
    Burstein & Heiles [AJ, 87, 1165 (1982)], new absolute magnitudes,
    distances, metallicities, and reddenings are derived for each star.
    The metallicities are determined with a revised calibration of the m1,
    (b-y) diagram based upon comparison to a compilation of recent
    spectroscopic abundances transformed to a common system.  The
    photometric abundances agree very well with the spectroscopic; the
    dispersion among the residuals for 58 giants is +/- 0.16 dex.  The
    dereddened indices are used to show that for red giants with [Fe/H] <
    -1.5, there is a well-defined relation in the c0, (b-y)0 diagram which
    exhibits only a weak dependence upon metallicity.  Use of the standard
    relations allows one to obtain reddening estimates for normal halo
    field giants and globular clusters in the appropriate metallicity
    range.