Abundance Analyses of Field RV Tauri Stars. VI. An Extended Sample

An abundance analysis is presented and discussed for a sample of 14 RV Tauristars. The present abundance data and those from our previous papers and byother workers are combined in an attempt to further understanding of thedust-gas separation process which afflicts many RV Tauri variables. We proposethat a star's intrinsic (i.e., initial) metallicity is given by thephotospheric zinc abundance. Variables warmer that about 5000 K and with aninitial metallicity [Fe/H] $\geq$ $-$1 are affected by dust-gas separation.Variables of all metallicities and cooler than about $T_{\rm eff} \simeq 5000$K are unaffected by dust-gas separation. The RV Tauri variables show a spreadin their C abundances with the lower boundary of the points in the C versus Znplane falling close to the predicted trend for giants after the firstdredge-up. The upper boundary is inhabited by a few stars that are carbon-rich.The O abundances in the mean follow the predicted trend from unevolved stars inline with the expectation that photospheric O abundance is unaffected by thefirst dredge-up. An evolutionary scenario involving mass loss by a first ascentor early-AGB red giant, the primary star of a binary, is sketched.Comment: 42 pages (including 13 figures), Accepted for Publication in Ap