STROMGREN PHOTOMETRY OF SHORT-PERIOD POPULATION-II CEPHEIDS

Observations of the v, b, and y bands of the Stromgren system are presented for 13 Cepheids of the disk and halo populations. Data for four additional stars in the literature are included. Values of [M/H] are derived for each star using theoretical v, b, y colors. The [M/H] values agree quite well with high dispersion investigations of three stars. A range of [M/H] values from -2.3 to +0.5 and greater is found. At least nine of the 17 Cepheids are found to have [M/H] values that are greater than found in any globular cluster that contains Cepheids. The highest [M/H] values may be due to uncertainties in circumstellar reddening of AU Peg and in the case of HR Aur, the likely presence of carbon bands in the spectrum. For the other stars whose [M/H] value is near zero it is possible that their atmospheres have been polluted by hydrogen-depleted material due to mass loss or mass transfer in a binary system.