Publications of the Astronomical Society of the Pacific
106: 1120-1133, 1994 November

       Studies of Large Amplitude delta Scuti Variables II: DY Herculis

                E. F. MILONE, W. J. F. WILSON, AND D. J. I. FRY

    Rothney Astrophysical Observatory, Department of Physics and Astronomy,
 University of Calgary, 2500 University Drive, NW, Calgary AB T2N 1N4, Canada
      Electronic mail: milone@acs.ucalgary.ca, wjfwilso@acs.ucalgary.ca,
                              fry@acs.ucalgary.ca

                                S. J. SCHILLER

              Physics Department, South Dakota State University,
                 Box 2219, Brookings, South Dakota 57007-0395
                   Electronic mail: SchilleS@mg.sdstate.edu

     
     ABSTRACT.  This is the second paper in a series on large-amplitude
     delta Scuti stars intended to determine Baade-Wesselink radii and
     luminosities with precision.  The first paper discussed our method of
     analysis and its application to EH Librae; in this we discuss the
     observations and analysis of DY Herculis.  Optical and infrared
     photometry and cross-correlated radial-velocity data have been
     obtained and analyzed.  Fourier representations for the UBVRIJHK light
     curves and for the radial-velocity curves were used to derive a value
     for the minimum radius for each of 60 combinations of flux and color
     index.  From these we adopt a mean value for the minimum radius of
     R_min = 2.77 +/- 0.20 Rsun.  When combined with effective
     temperatures from Breger et al. (1978), we find a mean bolometric
     luminosity of <L_B> = 21.70 Lsun and a mean absolute magnitude of
     <M_B> = 1.41.  The radial excursion is 0.149 Rsun.  We use the same
     procedure to improve our results for EH Librae, deriving R_min for
     each of 42 combinations of flux and color index, and obtain mean
     values of R_min = 2.62 +/- 0.19 Rsun, <L_B> = 24.56 Lsun and <M_B> =
     1.27.