THE ASTRONOMICAL JOURNAL    VOLUME 114, NUMBER 1, PAGE 341          JULY 1997

          ABUNDANCE ANALYSES OF TYPE II CEPHEIDS IN GLOBULAR CLUSTERS

                    GUILLERMO GONZALEZ AND DAVID L. LAMBERT

     Department of Astronomy, University of Texas, Austin, Texas 78712
                Electronic mail: gonzalez@astro.washington.edu


                                   ABSTRACT

     We have determined the photospheric compositions of five luminous F-G
     variables in globular clusters: V11 in M2, V42 in M5, V84 in M5, V2 in
     M10, and V17 in M28, three of which are classified as RV Tau variable
     stars.  Unlike the recent findings that the photospheres of field RV
     Tau variables have been altered by a gas-dust separation process, none
     of these stars, except possibly V2 in M10, show such signs. We suggest
     that either a smaller carbon abundance in the photosphere of a
     globular cluster RV Tau star (compared to its field analogues) might
     be a factor in the gas-dust separation process due to the lack of
     sufficient carbon grain formation, or the stellar winds and their
     efficacy as dust-grain separators is influenced by the metallicity of
     the stellar envelope which, unlike the photosphere, is never subject
     to alteration by a dust-gas separation. Our analysis is most complete
     for V84, for which we have estimated the abundances of 19 chemical
     elements. Compared to the other giants in M5, this star displays a
     very large excess of Na and a deficit of O. This finding is consistent
     with a recently proposed mechanism of Na production in the ON-cycling
     region of metal-poor RGB stars. The value of [Al/Fe] for V84 is also
     high (also consistent with ON-cycling), but a comparison with the
     other cluster giants cannot be performed until Al is measured in their
     spectra. The s-process elements are not significantly enhanced in the
     atmosphere of V84 relative to the other cluster members. (c) 1997
     American Astronomical Society.